Field of the Invention

This invention relates to an assembly of two box units, typically metal trays, that transform in their use as a fuel carrying box to a solid fuel burning camping stove.

Background to the Invention

When someone wishes to use solid fuel as a cooking heat source, a support for both the fuel and the pot above the fuel is required. However, the use of conventional solid fuel stoves that are also meant to be the containers of the fuel tablets can lead to a number of difficulties. Their folding design requires rivets or hinges in order to fold. Furthermore when folded out ready for use as a stove, a large area on the two non- folding sides is left open to the wind which can diminish the effectiveness of the flame or cause it to blow out altogether. The present invention is addressed at overcoming the problems of the prior art. Summary of the Invention

According to a first aspect, the invention provides a compact solid fuel camping stove comprising: a bottom box unit having sides and a base, with air holes in the sides; and a top box unit having sides and a base, with air holes in the base; wherein the bottom box unit and the top box unit are shaped such that the sides of one of the units can nest inside the sides of the other unit to form a closed box; and wherein the base of the top box unit can be placed onto on into the sides of the bottom box unit to form a stove.

According to a second aspect, the present invention provides the use of a compact solid fuel camping stove to store a solid fuel block and to heat a substance, wherein the stove comprises: a bottom box unit having sides and a base, with air holes in the sides; and a top box unit having sides and a base, with air holes in the base; wherein to store the fuel, the bottom box unit and the top box unit are positioned with the sides of one of the units nested inside the sides of the other unit to form a closed box and the solid fuel block is placed inside the block; and wherein to heat a substance, the base of the top box unit is placed onto or into the sides of the bottom box unit to form a stove, the solid fuel is placed onto the base of the top box unit and ignited, and the substance to be heated is positioned in a container on top of the sides of the top box unit.

According to a third aspect, the present invention provides a method of storing a solid fuel block and heating a substance, the method comprising the steps of: providing a compact solid fuel camping stove comprises: a bottom box unit having sides and a base, with air holes in the sides; and a top box unit having sides and a base, with air holes in the base; positioning the bottom box unit and the top box unit with the sides of one of the units nested inside the sides of the other unit to form a closed box and placing the solid fuel block inside the box to store the fuel; and then placing the base of the top box unit is onto or into the sides of the bottom box unit to form a stove, placing the solid fuel onto the base of the top box unit and igniting the fuel; positioning the substance to be heated in a container on top of the sides of the top box unit. To overcome the problems of prior art stoves, the present invention proposes a solid fuel camping stove which is made from two halves of a box, a bottom box unit and a top box unit. When the two box units are pressed facing together they can store the solid fuel tablets within the formed box. This is the storage configuration. If however the upper portion (top box unit) is facing the same way and placed on top of the bottom base unit, a stove can be made. This is the stove configuration.

In one embodiment the top box unit is rotated to sit diagonally on bottom box unit within cut-outs on that box's edges. In another embodiment the top box unit sits squarely within the bottom box unit. In both embodiments, air flows to the fuel from the box underneath (bottom box unit) via holes in the base of the upper portion (top box unit) and in the sides of the lower portion (bottom box unit) reducing the effect of direct wind. In other words, air passes through the holes in the side of the bottom box unit, and then changes direction to pass up through the air holes in the base of the top box unit, before being used in combustion of the fuel, so any excess wind speed that could otherwise cause inefficient burning is reduced. The direct line of air flow into the top box fuel burning unit is restricted. In this way the present invention provides a windproof stove, which offers protection against wind.

In addition to providing a very convenient way of storing solid fuels that makes excellent use of space, the stove of the present invention make it possible to achieve very clean and complete combustion, minimising soot deposition on a cooking container, and giving impressive energy transfer from the fuel to the substance to be heated. This is the case even in windy conditions. As the fuel is not in contact with the ground scorch marks are not present and the risk of ground contamination from the fuel is minimised. In one embodiment the present invention relates to a compact solid fuel camping stove comprising of a bottom box unit and a top box unit, which can be arranged from being a closed box when facing each other and pushed together, to then being a stove by facing the two halves the same way but juxtapositioned at forty five degrees to each other so one rests upon the other. The different external dimensions of the two box units allow the smaller half to nest inside the larger half to act as a storage container.

In a preferred embodiment, the larger box unit, which is preferably the bottom box unit, has four cut-outs on the leading edge of each of its sides so that when nested facing each other as a container they provide finger holds to enable the separation of the two box units in the storage configuration. In one embodiment the proportions of the cut-outs are such that when the box units are in the stove configuration, the four cut-outs provide a secure fit for the smaller top box unit when it is aligned at approximately forty five degrees to the larger bottom box unit to perform as a stove. In other words, the top box unit is placed onto the bottom box unit and rotated to sit diagonally on the bottom box unit within the cut- outs on that box's edges.

In another embodiment, in the stove configuration the base of the top box unit is placed onto or into the bottom box unit with the sides of the top and bottom box units aligned. In this embodiment indentations can be provided in the bottom box unit to support the base of the top box unit at a certain height above the base of the bottom box unit. The base of the top box unit is supported above the air holes in the sides of the bottom box unit, so the air can pass into those air holes and up into the top box unit through the holes in the base. If cut-outs are present in the bottom box unit, the indentations can be at the top edge of the cut-outs, bottom or below these so that they are covered by the sides of the top box unit and air only enters through the air holes.

Brief Description of the Drawings

An example of the invention will now be described by referring to the accompanying drawings in which:

Figure 1 shows the two halves of the box of a preferred embodiment of the invention are nested together to form a container, i.e. in the storage configuration;

Figure 2 shows the two halves of the box when pulled apart from being a container;

Figure 3 shows the two halves of the box when pulled apart from being a container, with the top box unit rotated to be placed onto the bottom box unit;

Figure 4 shows the two halves of the box nested together facing the same way and sitting diagonally to each other with the upper portion (top box unit) fitting within the cut-out edges of the lower portion (bottom box unit) to form the stove i.e. in the stove configuration;

Figure 5 shows the two halves of the box of a different preferred embodiment of the invention nested together to form a container, i.e. in the storage configuration; Figure 6 shows the two halves of the box of Figure 5, when pulled apart from being a container;

Figure 7 shows the two halves of the box of Figures 5 and 6 facing the same way and sitting aligned with one another to form the stove of one embodiment of the invention;

Figure 8 shows the two halves of the stove of Figures 7 separated; Figure 9 shows a close up of the area circled in Figure 8. Description

The present invention relates to a compact solid fuel camping stove. By compact camping stove, we mean that the stove is on a scale which can be carried and used by one person. Such a stove is typically used by campers and can be easily carried in a backpack.

Any type of solid fuel can be used with the camping stove, such as biomass (such as sticks and leaves etc.), but it is envisaged that the stove will be used with solid fuel blocks, such methyl ester or hexamine solid fuel blocks, as are well known in the art. It is particularly preferred to use the stove of the present invention with methyl, ethyl, propyl, or butyl esters of a C6-C14 carboxylic acid, of which methyl decanoate is the most popular, and is particularly advantageous as the fuel of solid fuel blocks. The C6-C14 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, as well as with hexamine blocks. Solid fuel blocks are often 20 mm high.

The stove comprises two sections, a bottom box unit and a top box unit, which when assembled in a nested position resemble a box, i.e. are approximately cuboid. In more detail, each box unit has sides and a base. The sides stand at approximately 90 degrees to the base and meet at their side edges. The sides and base are flat. There are usually four sides of equal height and each base is square or rectangular. The units of the present invention typically each have sides of length 50 to 100mm, or 60 to 80mm, and depth or 20 to 60mm, or 40 to 50mm.

The stove can transition between a storage configuration and a stove configuration. By stove we mean that the top box unit provides a combustion chamber with sufficient ventilation to burn solid fuel. During use the solid fuel is placed on the base of the top box unit. The units must be made of a material that is suitable for facilitating combustion. They are typically meal, such as steel or preferably are aluminium. In order to function as a stove the bottom box unit has air holes in at least one of the sides, preferably in all the sides. Each side usually has 1 to 20 air holes, preferably 5 to 15 air holes. The air holes are usually arranged at equal distances from each other around the sides i.e. are evenly spaced. The top box unit has air holes in the base. It can have any number of holes, but usually has 8 to 40 air holes, preferably 20 to 30 holes. In a preferred embodiment, the air holes are around the edges of the base. In use the fuel, usually a solid fuel block, is positioned on the base of the top box unit, preferably in the middle of the base, and so the air holes are optimally positioned around the solid fuel block to supply oxygen and aid complete combustion.

The air holes in the sides of the bottom box unit and base of the top box unit mean that the air flow can be controlled to achieve a very clean and efficient burn. In addition the stove of the present invention minimises soot deposition on a cooking container, and gives impressive energy transfer from the fuel to the substance to be heated. This is the case even in windy conditions because the fuel is protected from the wind by being inside the top box unit and benefiting from non-direct line of air flow.

The bottom box unit and the top box unit are shaped such that to provide a storage configuration the sides of one of the units can nest inside the sides of the other unit to form a closed box. The box is defined at one end by the base of the bottom box unit, at the other end by the base of the top box unit, and at the sides by the overlapping sides of the bottom box unit and the top box unit. This enclosed space can be used to store solid fuel when the stove is not in use. By closed box we mean a largely enclosed space. It is sufficiently enclosed to store solid fuel blocks securely. The space is not airtight, due, for example to the air holes in the base of the top box unit. In a second configuration, the stove configuration, the base of the top box unit can be placed onto or into the sides of the bottom box unit to form a stove. In use the fuel is placed into the top box unit and ignited, and the substance to be heated, such as water or food, is placed into a container, such as a saucepan, which is placed onto the sides of the top box unit. In one embodiment, the larger box unit, which is preferably the bottom box unit, has four cut-outs, one on the leading edge of each of its sides. In the storage configuration the cut-outs can be used as finger holds to help separate the box units. In one embodiment of the stove configuration, the cut-outs can be dimensioned so that they provide a secure fit for the top box unit when it is aligned at forty five degrees to the larger bottom box unit. In another embodiment in the stove configuration the top box unit is positioned with it's sides aligned with the bottom box unit.

In the aligned embodiment of the invention, indentations can be provided in the sides of the bottom box unit to support the base of the top box unit above the air holes in the sides of the bottom box unit. The indentations can be positioned as notches in the sides. Alternatively, the indentations can be provided at the top of cut-outs on 2 the sides. They can be 2 or more indentations per cut-out, but are preferably 2. The indentations can be positioned on all 4 sides of the bottom box unit or, more preferably, on 2 sides.

The aligned configuration, as shown in Figures 5 to 9, particularly Figure 7, is the most preferred. This has been designed to optimise efficiency of burn for a solid fuel block, and displays excellent performance. In particular, the solid fuel block burns cleanly, minimising soot deposited on the container.

As well as air holes to let air into the stove to facilitate combustion, the stove must allow exhaust gases to exit. The exhaust gasses comprise fully combusted products, typically carbon dioxide and water, oxygen depleted air and potentially fuel that is still combusting. Allowing exhaust gasses out of the combustion chamber allows turnover of air and sustains combustion. This can be achieved though the top of the top box unit if a cooking container is selected that does not completely cover the top of the stove. However, in a preferred embodiment, the top edge of at least one side of the top box unit is castellated to allow exhaust gases to escape, even if a cooking container is used that covers the whole top of the stove. One, two, three or four sides of the top box unit can be castellated.

In a preferred embodiment, two or three sides of the top box unit are castellated, and one or two are not. In this way extra wind protection can be provided, as the exhaust gases can easily exit through the castellations, but the blank sides can be positioned towards the wind to provide protection to the combusting fuel. The arrangement is also useful in a military setting as the flame cannot be seen from the blank sides which could be important for those trying to evade detection.

Turning now to the figures, in figure 1, the two halves of the box are in the storage configuration, nested together to form a container with the upper part of the stove (top box unit) 2 having less diameter than the lower part of the stove (bottom box unit) 1 which allows it to fit inside the lower part of the stove 1. The finger holds to enable someone to separate the two halves are revealed on the sides of the upper part of the stove 2 because of the four cut-outs 3 on the lower part of the stove 1.

Figures 2 and 3 show the box in the two halves with 1 being the lower or bottom box unit and 2 being the top box (fuel burner) unit. Air holes 6 in the base of the top fuel burner unit 2 draw air up from the lower base unit 1 which in turn draws air from its side holes 4 resulting in a non-linear air flow to make the stove windproof. Exhaust gases can escape through the notch's 5 (also called castellations) on the upper edge of the top burner unit 2.

Figure 4, shows the two halves of the box arranged to form the stove. The four cutouts 3 on the lower part of the stove (bottom box unit) 1 serve two purposes. The first being as finger holds when separating the two halves when they are acting as a container. The second use is as an aligning method to keep the two halves diagonal to each other when performing as a stove, as shown in Figure 4.

Figure 5 is similar to Figure 1 but an alternative example of the invention. Top box unit 2 is nested inside bottom box unit 1. Top box unit 2 has air holes in its base, 6. Bottom base unit 1 has air holes in its sides 4 and cut-outs 3.

Figure 6 shows the top box unit 2 with air holes 6 separated from the bottom box unit 1, with side air holes 4, cut-outs 3, and indentations 7, on which the top box unit rests in the stove configuration.

Figure 7 shows the stove configuration for the units of Figure 6. As can be seen, the top box unit 2 with air holes 6 sits inside the sides of the bottom box unit 1 on indentations 7. In this configuration during use solid fuel, preferably a solid fuel block is placed on the base of the top box unit, usually in the centre in the middle of the air holes. The fuel is ignited and burns. Air is drawn though air holes 4 in the bottom box unit and through air holes 6 in the top box unit to aid combustion. A substance to be heated is placed onto the sides of the top box unit, either directly or in a container. Exhaust gases escape through the castellations 5.

Figure 8 is similar to Figure 6 but with the top box unit inverted to form the stove rather than storage configuration. Figure 8 shows the top box unit 2 with air holes 6 and castellations 5 separated from the bottom box unit 1, with side air holes 4, cut- outs 3, and indentations 7. The circle in Figure 8 shows an area which has been expanded in Figure 9.

Figure 9 shows more clearly the indentations 7 in the bottom box unit 1. In the stove configuration, the top box unit rests on these indentations to so that the air flow through air holes 4 and 6 is not impeded.