WO2015025154A1

WO2015025154A1 - Portable cooking stove

Info

Publication number: WO2015025154A1
Application number: PCT/GB2014/052541
Authority: WO
Inventors: Eric Dennis Barford
Original assignee: Standard Brands UK Ltd
Current assignee: Standard Brands UK Ltd
Priority date: 2013-08-20
Filing date: 2014-08-19
Publication date: 2015-02-26
Anticipated expiration: 2016-02-20
Also published as: GB201314897D0

Abstract

A portable cooking stove is provided, comprising at least three sheet¬ like members (1, 15) including at least two perforated sheet-like members (1) and at least one blank sheet-like member (15); wherein each perforated sheet-like member has two faces (2), a top edge (3), a bottom edge (4) and two side edges (5), at least one exhaust opening (6) at or close to the top edge, and at least one air inlet (7) which is a perforation through the faces of the perforated sheet-like member (1); and wherein each blank sheet-like member (16) has two faces (2), a top edge (3), a bottom edge (4), two side edges (5), and no air inlet or exhaust openings; and wherein the sheet-like members (1, 15) are coupled together at their side edges.

Description

Portable Cooking Stove

Field of the Invention

This invention relates to cooking stoves, in particular, to lightweight, efficient, and readily portable outdoor cooking stoves that block light generated by the burning fuel from escaping the stove in a certain direction while also providing the burning fuel protection from wind and precipitation. The cooking stove is intended for use primarily by military forces, such as the dismounted infantry soldier, but also potentially by those undertaking general camping or other outdoor leisure pursuits such as backpacking, hiking or boating. The cooking stoves are further designed to collapse or dismantle to an easily storable flat pack, to be robust, and to make efficient use of solid-fuel blocks.

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 (under 150 grams) 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 to also carry their own fuel. To assist with keeping weight down, solid-fuel blocks can be used, such as hexamine blocks, trioxane blocks, solidified methyl decanoate blocks or 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. Certain solid fuels are waterproof, and further waterproof protection can be provided by means of a thin plastic wrapper.

To use such a portable cooking stove with 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. The problem encountered with solid-fuel blocks is that the characteristically aggressive burn leads 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, meaning that a greater number of fuel blocks must be carried by the operator. As such, it is of key importance to consider the efficiency with which any given stove arrangement can transfer the energy of the burning solid-fuel block into the cooking vessel.

A further important concern of tall flames, particularly to military personnel in proximity to an enemy, is that the light generated by the flames can act as a high visibility signal that may give away both the presence and the precise position of the stove operator. To remove the risk of such detection, it is desirable to block the light generated by the burning fuel, particularly in the direction of the enemy. This applies both to light emanating from any flames escaping the combustion chamber as well as the flames within the combustion chamber. A further high visibility signal that would ideally be prevented is smoke arising from incomplete combustion or the release of non-combusted volatiles.

As well as simply heating food and drink, portable cooking stoves provide the critical ability to sterilise food and water. With no consumer standards of performance set for portable stoves, the only benchmarks available are those used by military organisations. These tough standards and performance requirements specify that the stove must be lightweight, robust and capable of raising water from near freezing point to boiling and then to hold the boil for at least 5 minutes. For heating ready-to- eat, pre-packed meals, the stove must be able to raise a standard meal pack of 500 grams in weight plus 250 ml water to a minimum of 65°C. These standards clearly require that the stove plus fuel combination must be highly efficient.

Lightweight portable cooking stoves that can be dismantled and packed in a flat configuration are known in the prior art. Prior art stoves have generally been designed to utilise a number of fuels, most often to utilise burning wood. The efficiency with which prior art stoves can transfer heat from burning solid-fuel blocks to a cooking vessel is generally not optimal. The present invention aims to provide a portable, collapsible, modular cooking stove that improves the efficiency of heating foodstuffs in accordance with military criteria, while preventing a visible signal of smoke or light from flames from being displayed to an enemy. Extensive research was conducted by the inventor into designing a portable cooking stove that would prevent flames from leaving the combustion chamber and would prevent smoke from being generated. In addition, the inventor researched applying this technology to a portable cooking stove also capable of blocking light from penetrating certain walls and coupling joints of the stove walls.

Summary of the Invention

According to a first aspect, the present invention provides a portable cooking stove comprising at least three sheet-like members including at least two perforated sheetlike members and at least one blank sheet-like member; wherein each perforated sheet-like member has two faces, a top edge, a bottom edge and two side edges, at least one exhaust opening at or close to the top edge, and at least one air inlet which is a perforation through the faces of the perforated sheet-like member; and wherein each blank sheet-like member has two faces, a top edge, a bottom edge, two side edges, and no air inlet or exhaust openings; and wherein the sheet-like members are coupled together at their side edges. The provision of a stove with at least two sheet-like members that have one or more air inlets in the form of perforations provides a portable cooking stove that can increase the efficiency with which energy is transferred from burning fuel to a cooking vessel while also preventing the highly visible signals of tall flames and smoke. However, perforations provide a line of sight to the inside of the stove which means that a flame inside the stove can be visible. This could be particularly problematic in a military context. To block light generated by flames within the combustion chamber of the portable cooking stove from reaching the enemy, in addition to the perforated sheet-like members the portable cooking stove is assembled using one or more blank sheet-like members that have no air inlet or exhaust ports. By selecting a suitable number of such "blank" sheets for the size of the stove being constructed, and connecting the blank sheets side-to-side, the operator can block light from escaping in a particular direction while allowing suitable air input and exhaust output from the perforated sheet-like member with air inlet and exhaust ports.

Furthermore, the provision of a blank side to the portable cooking stove provides an enhanced level of protection from wind and precipitation, particularly by facing the blank side into the wind. Hence, by providing a stove that has sides with air inlets and exhausts and sides without, the competing desires to have efficient burning, while providing a means to hide the flames from view can both be achieved.

In a preferred embodiment of the invention a lattice of perforations is used. Using a lattice of perforations was found to restrict airflow into the stove in a manner that reduces the intensity with which fuel, such as a solid-fuel block, burns. This solves the problem of the intense burning of solid-fuel blocks leading to tall flames that do not remain underneath the cooking vessel. Careful investigation was required to ensure that the burn rate was lowered without leading to volatile organics not combusting at all (causing white smoke) or only partially combusting (causing black smoke). Furthermore, providing air inlets in the form of a lattice of perforations provides more protection to the burning fuel from gusts of wind than would be provided by fewer larger openings, as in prior art stoves.

Prior art stoves have in the past typically been designed to be compatible with a variety of fuels, primarily wood. As such, optimisation of portable cooking stoves specifically for burning solid-fuel blocks has not been investigated. Typical constructions of these prior art stoves have involved using tall structures. While this creates a large combustion chamber that goes some way to maintain more of the flame under the cooking vessel, the stoves are heavy and have a larger surface area from which to radiate heat.

In a preferred embodiment of the present invention, each sheet-like member defines a substantially square, rectangular or trapezium shape so that the assembled stove, which is the sheet-like members coupled together, defines a substantially cuboid, prism or pyramidal frustum shape. The coupled sheet-like members define the combustion chamber and also provide the structural support upon which to place the cooking vessel. The use of a pyramidal-frustum shaped cooking stove allows the heat from the burning fuel to be concentrated more centrally underneath the cooking vessel.

An important feature of the portable cooking stove is that it is modular. The stove may be assembled from a minimum of three sheet-like members. Should the cooking vessel be larger, the stove can easily be assembled from more sheet-like members, for example four, five or six sheets, to accommodate both more fuel and the larger cooking vessel. The stove is designed such that the increased number of solid-fuel blocks in the larger version of the stove maintains the optimal burn rate. The stove is assembled with an appropriate number of the blank sheet-like members selected to suit the size of the stove. For example with a three-sided stove only one blank sheet-like member would be used. With a four-sided stove one or preferably two blank sheet-like members would be used. A five-sided stove would need two blank sheet-like members, or three could be used. A six-sided stove would need two, but preferably three blank sheet-like members, and so on.

Each perforated sheet-like member has at least one exhaust opening at or close to the top edge. This is an important feature of the stove of the present invention as controlling the rate at which the exhaust fumes exit the stove assists with controlling the burn rate of the fuel. Allowing the exhaust fumes to vent too freely will allow the fuel to burn vigorously. Preventing the exhaust fumes from venting freely enough will extinguish the burning fuel. The inventor has found that providing at least one exhaust opening at or close to the top edge of each perforated sheet-like member can optimise the air flow through the stove, and hence optimise the efficiency with which the fuel burns. Preferably, the combined surface area of all the exhaust openings on a single perforated sheet-like member is up to 6 cm², more preferably up to 4 cm². In a preferred embodiment, the total exhaust opening area per perforated sheet-like member comprises two exhaust openings per perforated sheet-like member, wherein each exhaust opening has a surface area of up to 3 cm², preferably around 2 cm².

The size of the perforations and the density of air inlet perforations is also important. It has been found that the optimal airflow into the stove is achieved when each perforation has a surface area of 0.7 to 13 mm², preferably wherein each perforation is circular with a diameter of 1 to 4 mm, most preferably 1 to 3 mm.

It has further been found that the optimal airflow into the stove is achieved when the perforations of each perforated sheet-like member have a total surface area of 10 to 55 mm² per cm² of the face of the perforated sheet-like member, preferably 20 to 40 mm² per cm².

It has been found that the optimal airflow into the stove can be achieved when the perforations are arranged in a lattice that covers at least 60% of the surface area of the faces of each perforated sheet-like member. It is preferred that the lattice of perforations covers at least 70% or even 80% of the surface area of the faces of the perforated sheet-like members.

As mentioned above, using a lattice of perforations, rather than a small number of relatively large air inlets, has the advantage of giving better control of fuel burn rate, and better wind protection. By using a lattice of perforations, a large number of relatively small air inlets is provided, in contrast to prior art stoves.

It has been found that the airflow into the stove gives rise to an optimal burn rate of the fuel when the lattice of perforations has a grid size of at least 2 by 3 perforations, preferably at least 10 by 10 perforations, more preferably 15 to 25 by 15 to 25 perforations, as in preferred embodiments of the present invention.

In a preferred embodiment of the present invention, the coupling between side edges of the sheet-like members is reversible, so that the stove can be assembled and disassembled during use. Preferably when the stove is disassembled, the sheet-like members can be arranged to lie flat on top of one another. These embodiments allow the portable cooking stove to be stored and transported as a flat-pack, which is space- economic and can be conveniently stowed and carried. Such stoves can be rapidly and conveniently assembled, used and then returned to the flat-pack configuration after use.

According to a second aspect, the present invention provides a kit comprising at least two of the perforated sheet-like members and at least one of the blank sheet-like member according to the first aspect of the invention and one or more solid-fuel blocks. Examples of suitable solid-fuel blocks are hexamine blocks (e.g. as supplied by ESBIT Gmbh, Germany), trioxane blocks (e.g. as supplied to the USA military), solidified methyl decanoate blocks (as supplied by Zip Military Fuels, UK) or gelled alcohol packs. According to a third aspect, the present invention provides a method of heating a cooking vessel using the portable cooking stove according to the first aspect of the invention, wherein the portable cooking stove is assembled with the blank sheet-like members coupled side-to-side where there is more than one blank sheet-like member, and wherein a solid-fuel block is placed in the portable cooking stove and set alight, and a cooking vessel is placed onto the portable cooking stove.

According to a fourth aspect, the present invention relates to the use of a portable cooking stove according to the first aspect of the invention by military personnel to heat water or food. Use of blank sheet-like members has the advantage of blocking the fire from sight in one direction. This is particularly applicable in a military context.

Brief Description of the Drawings

Figure 1 relates to a preferred embodiment of the present invention, a kit of three perforated sheet-like members and three blank sheet-like members that can be used to assemble a three, four, five or six-sided stove.

Figure 2 relates to a preferred embodiment of the present invention, an assembled four-sided stove comprising two perforated sheet-like members and two blank sheetlike members shown without fuel or cooking vessel.

Figure 3 relates to a preferred embodiment of the present invention, an assembled six- sided stove comprising three perforated sheet-like members and three blank sheet-like members shown without fuel or cooking vessel.

Figure 4 relates to a preferred embodiment of the present invention, an assembled six- sided stove comprising three blank sheet-like members shown with a cooking vessel in the cooking configuration and showing that there is no line of sight to the combustion chamber.

Figures 5 relates to a preferred embodiment of the present invention, a folded hinge that couples sheet like members but blocks any line-of-sight through the hinge. Description

This invention relates to a portable cooking stove. By portable we mean that the stove can easily be carried by one person. As explained above, it is envisaged that the stove will primarily be used by military forces, such as the dismounted infantry soldier, but may also be used by those undertaking camping or other outdoor leisure pursuits.

The portable cooking stove comprises 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 is used, 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 the top edge will be uppermost.

The sheet-like members are 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.

The stove comprises sheet-like members coupled together at their side edges. 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 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 sheet-like members may, for example, be coupled using a slit substantially parallel to and within 10 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. The coupled sheet-like members can also be readily disassembled. By this we mean that after use, each sheet-like member of the portable cooking stove 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.

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.

It is preferred that the coupling mechanism chosen is capable of preventing light generated by the burning fuel from escaping from the stove through the coupling mechanism. That is, the coupling mechanism should substantially contain no straight- line gaps or, more preferably, no gaps, when assembled. Preferably the hinge is made from folds in the side edges of the sheet-like members that interlock.

The stove comprises at least three sheet-like members, and preferably comprises four to six sheet-like members, more preferably five 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. Optionally, the last coupling may be left open. 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 sheetlike 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. The portable cooking stove of the present invention includes sheet-like members of at least two different types.

A perforated sheet-like member comprises at least one air inlet which is a perforation through the faces. By perforations, we mean holes that extend through the sheet-like member from face to face. As explained above, these holes act as air inlets. There can be one air inlet, but preferably two or more, more preferably four or more air inlets are provided. The air inlets are below the exhaust opening.

In the present invention, the size of the perforations and the density of the perforations is also important. In particular, the inventor has found that performance can be optimised when each perforation has a surface area of 0.7 to 13 mm². Preferably each perforation is circular with a diameter of between 1 and 4 mm, preferably between 1 and 3 mm. The density of perforations is preferably such that, the perforations have a total surface area of 10 to 55 mm² per cm² of the face of the perforated sheet-like member. Preferably the perforations have a total surface area of 20 to 40 mm² per cm².

A perforated sheet-like member preferably comprises perforations arranged in a lattice which covers at least 60% of the surface area of the faces of the perforated sheet-like member. By lattice, we mean that the perforations are arranged in a grid. In other words, there is a plurality of perforations arranged in a series of lines, one above the other. The lattice of perforations provides regular spacing of the perforations. In the lattice there are at least 2 lines of perforations with at least 3 perforations in each line, i.e. a grid size of 2 by 3, with a total of at least six perforations. Preferably the lattice comprises a grid of at least 10 by 10, and most preferably between 15 to 25 by 15 to 25. As noted above, the inventor has surprisingly found that using a lattice of perforations can have the effect of controlling the air flow into the stove which can increase the efficiency of the fuel. The lattice of perforations also gives protection against gusts of wind. Prior art stoves which have used fewer but larger air inlets do not provide as much protection from the wind, or as much control over the burn rate. The lattice of perforations covers a substantial proportion of the face of the perforated sheet-like member. In particular, it covers at least 60% of the surface area of the faces of the sheet-like member. In a preferred embodiment, the lattice of perforations covers at least 70%, or preferably at least 80% of the surface area of the faces of the sheet-like member.

As well as inlets, which are provided by the perforations, it is important that the portable cooking stove has an air outlet. This is provided by at least one exhaust opening in each perforated sheet-like member which is at or close to the top edge. By close to the top edge, we mean that it is provided within 2 cm of the top edge. The exhaust opening is simply a hole (i.e perforation) in the sheet-like member, or notch cut into the otherwise substantially straight the top edge. Preferably the total surface area of the exhaust opening or exhaust openings is up to 6 cm², preferably up to 3 cm². In a preferred embodiment the exhaust openings are notches in the top edge of the perforated sheet-like member. In the most preferred embodiment the top edge of the perforated sheet-like member is castellated to provide two notches in the top edge which are exhaust openings and allow exhaust gases to escape the stove, when a cooking vessel is placed on top of the stove. The two notches can have a surface area of around 2 cm² each.

A blank sheet-like member is similar to the perforated sheet-like member in shape, size and coupling mechanism, but is differentiated in that the blank sheet-like member has no air inlet or exhaust ports. That is, the blank sheet-like member has a substantially blank face.

Constructing a portable cooking stove using one or more of the blank sheet-like members has an effect on the airflow characteristics of the assembled portable cooking stove. To achieve optimal burn characteristics of the fuel, the air inlet and exhaust ports of the perforated sheet-like member must be designed to achieve a satisfactory air flow for the whole stove, taking into account that some of the faces of the stove are blank. Using at least one blank sheet-like member has the advantage that light generated by the burning fuel can be prevented from escaping the portable cooking stove in the direction that the blank sheet-like member is facing. That is, the material of the blank sheet-like member acts as a physical barrier to the penetration of light and the face of the sheet-like member contains no holes through which light can pass.

Furthermore, the blank sheet-like member has a flat top and bottom edge that forms a close fit with a cooking vessel and the ground respectively, further acting to prevent the escape of light. Yet further, the coupling mechanism used to couple the sheet-like members together is preferably also designed to prevent the escape of light. The blank sheet-like member also acts as a physical barrier to the entry of wind and precipitation into the combustion chamber of the portable cooking stove. That is, when the stove is arranged such that the blank sheet-like member is facing into the wind, the wind and rain is prevented from extinguishing the fuel.

The smallest embodiment of the portable cooking stove, the three-sided portable cooking stove, requires only a single blank sheet-like member to present a blank face in a single direction. A four-sided portable cooking stove requires only a single blank sheet-like member to present a blank face in a single direction but realistically benefits from having two blank sheet-like members coupled side-to-side with the apex of the coupling facing the direction of the enemy or the wind. A five-sided portable cooking stove requires two blank sheet-like members, coupled side-to-side, to present a blank face in a single direction, but may have three blank sheet-like members. A six-sided portable cooking stove requires two, but preferably three, blank sheet-like members, coupled side-to-side, to present a blank face in a single direction.

As the portable cooking stove is modular in nature, the operator can choose which size of stove to assemble depending on what size of cooking vessel is required.

According to a second aspect, the present invention provides a kit comprising at least three sheet-like members according to the first aspect of the invention and one or more solid-fuel blocks. Examples of suitable solid-fuel blocks are hexamine blocks (e.g. as supplied by ESBIT Gmbh, Germany), trioxane blocks (e.g. as supplied to the USA military), solidified methyl decanoate blocks (as supplied by Zip Military Fuels, UK) or gelled alcohol packs.

According to a fourth aspect, the present invention provides a method of heating a cooking vessel using the cooking stove of the first aspect of the invention, wherein the portable cooking stove is assembled with the blank sheet-like members coupled side- to-side where there is more than one blank sheet-like member, and wherein a solid- fuel block is placed in the portable cooking stove and set alight, and a cooking vessel is placed onto the portable cooking stove. The assembled portable cooking stove can then be positioned such that the blank sheet-like members are facing a certain direction, for example, towards an enemy. As the solid-fuel block burns, air is drawn in through the lattice of perforations of the perforated sheet-like members, maintaining combustion. The coverage of a substantial area of the sheets by a lattice of perforations restricts the airflow, resulting in a slower rate of combustion. As the solid-fuel block burns, air also exits from the exhaust openings of the perforated sheet- like members. Careful control of airflow in and out of the combustion chamber ensures that, even though combustion is slowed, there is enough airflow to ensure full combustion occurs. This means that, primarily, the efficiency of heat transfer to the cooking vessel is high, that there is no black or white smoke generated, that flames do not exit the combustion chamber and also that the burning fuel does not extinguish. Furthermore, the light generated by the burning fuel within the combustion chamber does not exit the portable cooking stove in the direction that the one or more blank sheet-like members are facing.

Detailed Description of the Drawings

Figure 1 shows a preferred embodiment of the perforated sheet-like members, 1, and blank sheet-like members, 15, that can be assembled to form the portable cooking stove of the present invention. Figure 1 shows the sheet-like members, 1 and 15, having two faces, 2, a top edge, 3, a bottom edge, 4 and two side edges, 5. A protruding edge, 8, extends from one side edge, 5, which has slits, 9. The opposite side edge, 5, of the sheet-like members, 1, have one open slit, 10 and one closed slit, 11, for coupling individual sheet-like members, 1. The perforated sheet-like members, 1, comprise two exhaust openings, 6, which are in the form of a castellated top edge, 3. The perforated sheet-like members, 1, also have a lattice of perforations, 7, covering a substantial portion of the faces, 2. The blank sheet-like members, 15, have no air inlets or exhaust outlets.

The sheet-like members, 1 and 15, shown in figure 1 can be coupled at their side edges, 5. The coupling of two perforated sheet-like members, 1, with two blank sheetlike members, 15, wherein the two blank sheet-like members, 15, are coupled side-to- side, forms a four-member portable cooking stove, 12, as shown in figure 2.

The coupling of three perforated sheet-like members, 1, with three blank sheet-like members, 15, wherein the blank sheet-like members, 15, are coupled side-to-side, forms a six-member portable cooking stove, 13, as shown in figure 3.

Figure 4 shows the portable cooking stove, 13, of figure 3 in use with a cooking vessel, 14, placed in the cooking configuration. The cooking vessel, 14, has a flat bottom that lies flush with the top edge, 3, of the blank sheet-like member, 15, which blocks any line-of-sight to the combustion chamber in the direction that the blank sheet-like members face.

Figure 5 shows a coupling mechanism that is a hinge, 16, comprising interlocking folded side edges, 5, of the sheet-like members, 1 and 15. In particular, figure 5 shows the coupling of a perforated sheet-like member, 1, with a blank sheet-like member, 15. This hinge, 16, is particularly advantageous in that it contains no gaps that provide a line-of-sight to the combustion chamber.

Claims

1. A portable cooking stove comprising at least three sheet-like members including at least two perforated sheet-like members and at least one blank sheet-like member;

wherein each perforated sheet-like member has two faces, a top edge, a bottom edge and two side edges, at least one exhaust opening at or close to the top edge, and at least one air inlet which is a perforation through the faces of the perforated sheetlike member; and

wherein each blank sheet-like member has two faces, a top edge, a bottom edge, two side edges, and no air inlet or exhaust openings; and

wherein the sheet-like members are coupled together at their side edges.

2. The portable cooking stove according to claim 1, wherein each sheet-like member defines a substantially square, rectangular or trapezium shape so that the assembled portable cooking stove defines a substantially cuboid, prism or pyramidal frustum shape.

3. The portable cooking stove of claim 1 or 2, wherein the portable cooking stove consists of four sheet-like members including two perforated sheet-like members or the portable cooking stove consists of five or six sheet-like members including two or three perforated sheet-like members, preferably wherein the portable cooking stove consists of five sheet-like members including two or three perforated sheet-like members.

4. The portable cooking stove of any preceding claim, wherein for the perforated sheet-like members each exhaust opening has a larger surface area than each perforation, preferably wherein the total surface area of the exhaust opening or exhaust openings is up to 6 cm² per perforated sheet-like member, preferably around 3 cm² per perforated sheet-like member.

5. The portable cooking stove according to any preceding claim, wherein the exhaust openings are notches in the top edge of each perforated sheet-like member, preferably wherein the top edge of each perforated sheet-like member is castellated.

6. The portable cooking stove according any to preceding claim, wherein the sheet-like members are constructed from aluminium, titanium, nickel, copper, mild steel, stainless steel or brass.

7. The portable cooking stove according to any preceding claim, wherein each perforated sheet-like member comprises a lattice of perforations which covers at least 60% of the surface area of the faces of the perforated sheet-like member, preferably wherein each perforated sheet-like member comprises a lattice of perforations which covers at least 80% of the surface area of the faces of the perforated sheet-like member.

8. The portable cooking stove according to claim 7, wherein the lattice of perforations of each perforated sheet-like member has a grid size of at least 2 by 3 perforations, preferably at least 10 by 10 perforations, more preferably 15 to 25 by 15 to 25 perforations.

9. The portable cooking stove according to any preceding claim, wherein the perforations of each perforated sheet-like member have a total surface area of 10 to 55 mm² per cm² of the faces of the perforated sheet-like member, preferably 20 to 40 mm² per cm².

10. The portable cooking stove according to any preceding claim, wherein the perforations of each perforated sheet-like member have a surface area of 0.7 to 13 mm², preferably wherein each perforation is circular with a diameter of 1 to 4 mm, preferably 1 to 3 mm.

11. The portable cooking stove according to any preceding claim, wherein the coupling between the side edges of the sheet-like members is reversible so the portable cooking stove can be assembled and disassembled during normal use, preferably wherein when the portable cooking stove is disassembled, the sheet-like members can be arranged to lie flat on top of one another.

12. The portable cooking stove according to claim 11, wherein the sheet-like members have a slit substantially parallel to and within 10 mm of the side edges, wherein the sheet-like members are coupled at their side edges through the interlocking of complementary slits.

13. The portable cooking stove according to claim 11, wherein the sheet-like members are coupled by hinges.

14. The portable cooking stove according to claim 13, wherein the hinges do not allow light to escape from the portable cooking stove through the hinge.

15. A kit comprising at least three sheet-like members including at least two perforated sheet-like members and at least one blank sheet-like member;

one or more solid-fuel blocks.

16. A kit according to claim 15 wherein the solid-fuel block comprises hexamine, trioxane, or solidified methyl decanoate, preferably wherein the solid-fuel block comprises methyl decanoate.

17. A method of heating a cooking vessel using the portable cooking stove of any of claims 1 to 14, wherein the portable cooking stove is assembled with the blank sheet-like members coupled side-to-side where there is more than one blank sheet-like member, and wherein a solid-fuel block is placed in the portable cooking stove and set alight, and a cooking vessel is placed onto the portable cooking stove.

18 Use of a portable cooking stove according to any of claims 1 to 14, by military personnel to heat water or food.

19. A stove substantially as shown in figures 1 to 5, and/or as described herein.