Field of Invention

The present invention relates to a windshield for a portable stove.

Portable stoves are often carried in rucksacks, and are used for cooking food or boiling water for a beverage or dehydrated food packages, for example. A portable stove requires a supply of fuel that is typically ignited by a user while being outdoors where the stove is exposed to the elements, such as strong winds. These elements may prevent ignition of the stove or may extinguish the flames once ignited, such that it is difficult to operate the portable stove effectively.

It is also known that military personnel are often requested to avoid using portable stoves on operations because using or igniting such a stove would give off visible light that can be detected by adversaries to identify the presence and position of the user. However, in emergency circumstances, such as where a person is suffering from hypothermia or where the only way to obtain water in colder climates is by heating ice or snow, it may be necessary to use a portable stove regardless of the risk of being seen.

It is desirable to provide a portable stove that addresses the disadvantages mentioned above.

Summary of the Invention

According to an aspect of the present invention, there is provided a windshield for a portable stove. The windshield may comprise a sidewall that at least partly encloses a space suitable for receiving a burner assembly of the portable stove. The sidewall may have at least one port opening. The windshield may have at least one port shutter that is moveable between a closed position, at which the port opening is at least partly blocked by the port shutter, and an open position, at which the port opening is, e.g. fully, open for allowing access to the enclosed space through the sidewall. When a burner assembly of a portable stove, such as a gas burner, is received and enclosed within the windshield, the burner assembly will be protected from weather elements by the sidewall. Additionally, the port openings allow a user to access the burner assembly while it is placed within the space that is enclosed (and protected) by the windshield, to aid ignition of the burner assembly. This not only increases the stove’s usability in harsh weather, but also facilitates more efficient use of fuel, e.g. gas, as compared to hypothetical arrangements in which the fuel is lost to the atmosphere if not ignited within a given timeframe. The port shutters may provide additional shielding, when in the closed position. For example, the port shutters may reduce the risk of wind or rain passing through the port opening and extinguishing the flames once ignited.

The at least one port shutter may cover its corresponding port opening entirely, when in the closed position. The port shutter may have the same shape as the shape defined by the port opening and may have the same surface area as the shape defined by the port opening.

The sidewall and/or the at least one port shutter may be opaque to visible light. In this way, the intensity of visible light emitting from the windshield is reduced or even eliminated when using the burner assembly. This may enable a burner assembly or stove that is enclosed within the windshield to be used with a reduced risk of being detected.

The at least one port shutter may be offset from its corresponding port opening or sidewall. This may allow airflow or exhaust gas through the port opening, while still shielding the burner assembly or stove from harsh weather conditions and reducing the intensity of visible light emitting through the windshield.

Alternatively, the at least one port shutter may have a zero offset from its corresponding port opening or sidewall.

The port shutter may comprise one or more apertures that allow air and exhaust gas to flow therethrough. This may allow airflow or exhaust gas through the port opening, while still shielding the stove and reducing the intensity of visible light through the windshield.

The windshield may further comprise a bottom wall (i.e. a base) positioned below the space suitable for receiving the burner assembly of the portable stove.

The bottom wall (base) may be shaped to define, together with the sidewall, a reservoir for containing fuel. This may provide the user with the ability to burn alternative fuels using the windshield, such as solid, gel or liquid fuel, in circumstances where a burner assembly is not present, for example.

The bottom wall (base) may comprise an aperture for receiving the burner assembly therethrough.

The rim of the aperture may comprise at least one notch.

The windshield may comprise a top wall (i.e. a lid) for supporting a food or liquid receptacle above the space enclosed by the sidewall. In this way, the windshield itself may be suitable for use as a portable stove in that a receptacle to be heated can be supported above the heating element of the burner assembly. This may obviate the need for a user, such as a soldier, to carry a separate stove.

The top wall (lid) may be shaped such that it comprises a planar surface having an aperture for allowing thermal energy from within the enclosed space to directly heat the receptacle through the aperture, when the receptacle is supported on the planar surface.

The top wall (lid) may be shaped such that it further comprises a ridge extending from the planar surface along the perimeter of the planar surface.

The top wall (lid) may comprise a section which extends parallel to the sidewall and overhangs a portion of the sidewall that includes one or more venting holes. The windshield may comprise a plurality of legs pivotably connected to the sidewall. The plurality of legs may be adjustable between a first angular position and a second angular position with respect to the sidewall, to position the windshield between two different height positions.

Each leg may comprise a first arm and a second arm that are connected at a base. The first arm may have a first end opposite the base which is pivotably connected to the sidewall at a connection point. The sidewall may comprise an indexer having a first lug that is fixed at a first circumferential position about the connection point. The indexer may have a second lug that is fixed at a second circumferential position about the connection point. The second arm may have a free end which is configured to be rotated about the connection point to engage the first lug, such that the leg may be held at the first angular position. The free end may be configured to be resiliently deflectable from the first lug to allow further rotation of the free end towards the second lug, for engaging the second lug such that the leg is held at the second angular position.

The sidewall may have a first port opening for receiving a match. The sidewall may have a second port opening for receiving a holder that retains a match striker. The first and second port openings may be arranged on the sidewall at an angle with respect to one another, such that the respective axis of the first and second port openings may converge to allow the match and the match striker to be brought into contact within the enclosed space.

According to a further aspect of the invention, there is provided a kit of parts comprising the windshield described above, a match and a holder that retains a match striker.

The sidewall may have a first port opening for receiving the match and a second port opening for receiving the holder that retains a match striker. The first and second port openings may be arranged on the sidewall at an angle with respect to one another, such that the respective axis of the first and second port openings converge to allow the match and the match striker to be brought into contact within the enclosed space. The first port opening and the head of the match may have an engineering fit, e.g. a, preferably loose running, clearance fit. The second port opening and the holder may have an engineering fit, e.g. a, preferably loose running, clearance fit.

According to a further aspect of the invention, there is provided a kit of parts comprising the windshield described above and a burner assembly of a portable stove.

The burner assembly may comprise a spring lock mechanism that is configured to removably attach the burner assembly to a rim of the aperture.

The spring lock mechanism may comprise two or more resiliently deflectable arms arranged circumferentially about a longitudinal axis of the burner assembly. Each arm (of the two or more arms) may have a notch on a radially outer surface of the arm for engaging a respective (e.g. one of the at least one) notch on the rim of the aperture. The two or more arms may be biased radially outwards from the burner assembly.

The spring lock mechanism may be configured to attach the burner assembly to the rim of the aperture in an inverted orientation.

The depth of the windshield to the rim of the aperture may be larger than a longitudinal extent between the notches on the resiliently deflectable arms and a distal end of the burner assembly that is opposite to an end of the burner assembly corresponding to a burner element of the burner assembly.

The burner assembly may comprise an oval-shaped burner element.

The burner assembly may comprise a cap for covering the burner element. Capping the burner element prevents the burner element from getting clogged with alternative fuel residue, if present.

The Applicant considers that the burner assembly described herein is novel and inventive in its own right. Therefore, according to a further aspect, there is provided a burner assembly for use with the windshield of the technology described herein. The burner assembly may comprise any one or more (or all) of the features of the burner assembly as described herein and according to any one of the above statements.

The Applicant also considers that the leg and indexer arrangement of the windshield described herein is novel and inventive in its own right. Therefore, according to a further aspect, there is provided a kit comprising: a leg for being pivotably connected to a wall of a component, such as a windshield; and an indexer for being fixedly connected to the sidewall, wherein the indexer is configured to hold the leg in at least one angular position with respect to the wall. The leg and indexer may comprise any one or more (or all) of the features of the leg and indexer as described herein and according to any one of the above statements. For example, the indexer may comprise a first and/or second lug(s) for being arranged at different circumferential positions about a connection point of the leg and wall. The leg may also be pronged, as will be described in further detail below.

The Applicant also considers that the holder for a match striker is novel and inventive in its own right. Therefore, according to a further aspect, there is provided a holder for a match striker. The holder may comprise any one or more (or all) of the features of the holder as described herein and according to any one of the above statements.

The holder may include a base wall and two, e.g. parallel, sidewalls arranged on opposite sides of the base wall in the transverse direction, to define a C-shape in cross section. At a first longitudinal end of the holder may be an end wall extending (e.g. perpendicularly) from the base wall (and e.g. parallel with the sidewalls). At a second longitudinal end opposite the first end, the holder may have an opening for allowing a striker to be slidingly received within the space enclosed by the sidewalls and end wall. The sidewalls may include one or more grooves for engaging the sides of the striker to retain the striker in the holder. The end wall may act as a blocker to prevent further passage of the striker. The striker holder may have an inner width of at least 7mm between the two sidewalls and a length along a longitudinal direction of the base that is at least 50 mm for receiving a striker of the same width and length.

The skilled person will appreciate that except where mutually exclusive, a feature or parameter described in relation to any one of the above aspects may be applied to any other aspect. Furthermore, except where mutually exclusive, any feature or parameter described herein may be applied to any aspect and/or combined with any other feature or parameter described herein.

Brief Description of Drawings

Embodiments will now be described by way of example only, with reference to the Figures.

Figure 1 is an exploded view of a windshield according to the present invention.

Figure 2 shows a first possible arrangement of the windshield when deployed to burn gas fuel.

Figure 3 shows a first possible arrangement of the windshield when in a stowed configuration.

Figure 4 shows a first possible arrangement of the windshield when deployed to burn liquid, gel or solid fuel.

Figure 5 shows a view of a striker assembly component for use with the windshield of the present invention.

Figure 6 shows an above view of a first possible arrangement of the windshield when the gas burner is being lit.

Figure 7 shows a first possible arrangement of the windshield adjusted to different height positions.

Figure 8 shows a cross sectional view of a first possible arrangement of the windshield, when deployed to burn gas fuel. Figures 9 and 10 show different views of a first possible arrangement of the windshield and burner assembly, illustrating the removal of the burner assembly from the windshield.

Detailed Description

With reference to Figures 1 to 4, there is generally shown a windshield 30 and a burner assembly 50 of a portable stove, in accordance with the technology described herein.

As best shown in Figure 1 , the windshield is in the form of a sidewall 1 , a top wall (i.e. a lid) 2 and a bottom wall (i.e. a base) 21 that together enclose a space 100 in which the burner assembly 50 of the portable stove can be at least partly received. The bottom wall 21 comprises an aperture 21 1 for receiving the burner assembly 50 therethrough. The sidewall 1 , top wall 2 and the bottom wall 21 are opaque to visible light. The sidewall 1 and the bottom wall 21 may be formed of a single piece of folded sheet metal, or may be formed of separate parts that have been attached using conventional methods known in the art. The top wall 2 may also be formed of a single piece of sheet metal and may be attached to the sidewall 1 by spot welding, or any other suitable attachment means known in the art.

The sidewall 1 itself comprises a main body having four planar inner surfaces that circumferentially surround the space 100 and extend substantially perpendicularly to the bottommost surface 98 of the bottom wall 21 (i.e. the surface that is furthest from the top wall 2). The main body surfaces are also arranged perpendicularly to the top wall 2, such that the windshield 30 defines a substantially cuboidal space 100 therein.

The top wall 2 has a planar surface 202 for supporting a cooking receptacle or mug (not shown) above the burner assembly 50, such that the windshield itself can serve as a stove. The planar surface 202 may have an, e.g. central, aperture 200 for allowing heat from the burner assembly to directly heat the cooking receptacle.

The size and shape of the aperture 200 can be selected and designed to accommodate a mug. For example the aperture 200 may be in the form of an oval shaped aperture, for receiving a correspondingly (e.g. oval-) shaped mug, such as a so-called“Crusader Cup Canteen” supplied by BCB International (NATO Approved NSN-6850-99-798-5980 and NSN-8465-99-721 -3131 ). The top wall 2 also includes a ridge 201 extending from the planar surface 202 along the perimeter of the planar surface 202, for reducing the extent of sliding of the cooking receptacle on the planar surface. The top wall may be shaped in this manner by appropriately folding or stamping a sheet metal using techniques known in the art.

The perimeter of the planar surface 202 may be substantially rectangular (albeit with rounded corners) having a dimension that is suitable to receive a so-called“mess tin”, which is a known type of cooking receptacle having a rectangular base and rounded corners. In particular, the top wall 2 may be may be suitable for snugly receiving a mess tin having a length of approximately 18cm and a width of approximately 13.7cm. This may be achieved by manufacturing the top wall 2 such that the apex of the ridge 201 defines a substantially rectangular shape having a corresponding length of approximately 18cm and width of approximately 13.7cm. The transition between the planar surface 202 and the apex of the ridge 201 may also or instead be shaped to conform to the shape of the rounded corners at the base of the mess tin.

The aperture 200 in the top wall 2 is substantially oval in shape in order to maximise the amount of heat distributed across the base of a cooking receptacle supported on the planar surface 202, as compared to a hypothetical arrangement in which the aperture is circular or square.

The sidewall 1 has a plurality of (in this example eight) protrusions or“posts” 102 extending from the sidewall surfaces, e.g. in the same plane as the sidewall surfaces, on which the top wall 2 is supported. The top wall 2 is in embodiments spot welded to the sidewall 1 , e.g. at positions corresponding to the protrusions 102. The gaps between the protrusions 102 and the top cover 2 define venting holes 101 for exhaust gases produced by the burning element in use.

The top wall 2 includes, on the side of the ridge 201 that is opposite to the planar surface 202, a surface 203 extends parallel to and overhangs the sidewall 2 of the windshield 30 such that it overhangs the venting holes 101 between the protrusions 102. The surface 203 may be offset from the sidewall to allow exhaust gas from combusted fuel to flow out between the windshield 1 and top wall 2, while minimising the intensity of light emitted from the enclosed space 100.

The sidewall 1 may include a first port opening 103 and a second port opening 104 arranged on perpendicular surfaces of the sidewall 1 , which allow access to the space 100 enclosed by the windshield 30. Attached to the sidewall 1 is a first port shutter 6 for opening and blocking the first port opening 103 and a second port shutter 5 for opening and blocking the second port opening 104. The first and second port shutters 6, 5 are suitable for opening and blocking their respective first and second port openings 103, 104 in that they are, e.g. pivotably, attached, e.g. by a rivet joint, to the sidewall 1 , such that each shutter is moveable (rotatable about the pivoted connection) between a closed position, at which the shutter is in a position that restricts (and e.g., entirely blocks or closes) access to the space 100 through the corresponding port opening, and an open position, at which the shutter is in a position that does not restrict access to the space 100 through the corresponding port opening.

Attached to the sidewall 1 are a plurality of (in this example four) legs 4 that may extend downwardly in a direction away from the top wall 2, so that the windshield 30 can stand on a surface at an elevated position, as best shown in Figure 2. The plurality of legs 4 may be pivotably connected to the sidewall 1 , e.g. by a rivet, such that they can be rotated to a position at which the entire length of the legs 4 are adjacent, and e.g. flush with, the sidewall, as best shown in Figure 3, for ease of stowing the windshield within a rug sack. This may avoid the legs snagging when stowed in a rucksack

In the examples shown in the drawings, the burner assembly 50 is configured to burn fuel in the form of gas. The gas may be supplied from a canister 40 through a gas flow control module 17 to the burner assembly 30 and in particular a burner element 14 which has apertures through which gas emerges when the burner assembly is in use. The burner element 14 may have an oval shape to maximise the distribution of heat emitting therefrom, although in other examples the burner element may be circular, square or rectangular, for example. The gas can flow from the control module 17 through a gas hose 16, a fuel supply attachment (in this example a gas diverter) 7, a gas nozzle 8 and a mixing tube 10 where the gas mixes with air. The gas and air mix can then go through a burner attachment 13 and out through apertures in the burner element 14. The burner attachment 13 and burner element 14 may be supported by a, e.g. oval-shaped, burner base 12 that is positioned on a base light shield 1 1. The gas hose 16 may be removable from the fuel supply attachment 7.

The burner element 14 and gas diverter 7 are at longitudinally opposite ends of the burner assembly 30, a first end corresponding to the burner element 14 and a second end corresponding to gas diverter 7. It will be appreciated that the burner assembly 50 is shown in Figure 1 in an inverted orientation where the direction of gas flow through from the gas diverter 7 to the burner element 14 is opposite to the direction from the bottom wall 21 to the top wall 2 of the windshield 30. However, in use, the burner assembly will be oriented in an upright configuration such that the direction of gas flow from the gas diverter 7 to the burner element 14 is substantially the same direction as that from the bottom wall 21 to the top wall 2. In other words, the burner assembly 30 will be oriented in use such that the burner element 14 faces the aperture 200 in the planar surface 202 of the top wall 2. In that configuration, at least the burner element 14, base light shield 1 1 (if present) and burner base 12 (if present) are located within the space 100 enclosed by the windshield 1 .

In the stowed configuration, as shown in Figure 3, the gas hose 16 and gas flow control module 17 may be wrapped or stowed around a burner element 14 of the burner assembly 50 (which is described further below) within the windshield 30. The gas hose 16 may be relatively rigid, to push against the inside of the windshield 1 to prevent rattling of the component when the windshield 30 is moved.

As best shown in Figures 4 and 8, the windshield may still be used as a stove where a gas supply or burner assembly is not present or available. For example, the windshield may be suitable for retaining fuel in the form of solid, liquid or gel fuels to be used as an alternative fuel source. The alternative fuel can be positioned onto the bottom wall 21 of the windshield 1 .

In the arrangement of Figure 8, which shows the windshield 30 and burner assembly 50 in cross-section, the bottom wall 21 is shaped to define, together with the sidewall 1 , a reservoir 210 for containing the alternative fuel. As can be seen, the sidewall 1 and the bottom wall 21 are shaped to define a substantially U-shaped reservoir in cross-section. The shape of the reservoir is defined by a first inner surface of the sidewall 1 , a second inner surface of the bottom wall 21 that defines the base of the reservoir, and a third inner surface 212 of the bottom wall 21 that extends away from the base of the reservoir 210 in a direction substantially in line with the first inner surface of the sidewall 1 . The reservoir extends circumferentially about the aperture 21 1 for receiving the burner assembly 50, such that the reservoir 210 can be said to be annular in that it has a ring-shape when viewed from above. The depth of the reservoir 210 may be defined by the height 214 of the third inner surface 212 of the reservoir 210. The third inner surface 212 defines a radially inner wall of the reservoir, wherein the radially inner surface 212 has a flange 213 at its upper end that defines the rim of the aperture 21 1 .

The reservoir 210 is suitable for receiving and retaining a liquid or gel— based fuel substance, which can then be ignited for use to heat a receptacle that may be supported on the top wall 2. A burner cap 15 may include one or more slots or grooves 150 on its inner surface for engaging corresponding tongues 1 10 on the light shield 1 1 (as shown in Figure 1 ) such that the cap can be held in place. The cap 15 may be used to prevent a build-up of fuel residue in the apertures of burner element 14.

The burner assembly may be configured with a gap Y between the bottom wall, particularly the flange 213, and the light shield 1 1 to allow airflow into and out of the space 100 enclosed by windshield 30. In an alternative embodiment, however, there may not be a bottom wall (i.e. a base) 21 to the windshield 30 (or corresponding burner assembly 50) such that the windshield 30 can be positioned around separate gas burner or alternative fuel stove.

As will now be described with respect to Figures 5 and 6, the first port opening 103 is circular and has a diameter that is suitable for allowing a fire-lighting match 20 to pass therethrough unrestricted. The second port opening 104 is rectangular to allow a corresponding match striker 19 to pass therethrough.

In this example, the first port opening 103 has a diameter of, e.g., at least 3mm such that it is suitable for allowing the head of a fire-lighting match 20 to pass therethrough unrestricted. The match 20 may be of the type supplied in a standard British Army ration pack (NATO APPROVED: NSN 9920-99-966-9432), having a head diameter of approximately 3mm. The match (first) port shutter 6 may be moved in a clockwise direction to allow the match 20 to fit through the side wall of the windshield 1 through the opening 103.

The second port opening 104 is in this example rectangular to allow a correspondingly shaped holder for a match striker 19 to pass therethrough. In particular, the striker 19 is retained within a striker holder 18, which, as best shown in Figure 5, has a C-shaped cross section. The holder may include a base wall and two parallel sidewalls arranged on opposite sides of the base wall in the transverse direction, to define the C-shape in cross section. At a first longitudinal end of the holder may be an end wall extending perpendicularly from the base wall. At a second longitudinal end opposite the first end, the holder may have an opening for allowing a striker to slide within the space enclosed by the sidewalls and end wall. The sidewalls include one or more grooves for engaging the sides of the striker to retain the striker in the holder. The end wall acts as a blocker to prevent further passage of the striker. The striker holder may have an inner width of at least 7mm between the two sidewalls and a length along a longitudinal direction of the base that is at least 50 mm for receiving a striker of the same width and length. Correspondingly, the striker (second) port shutter 5 may be moved in an anticlockwise direction to allow the match striker 19 to fit through the sidewall of the windshield 1.

As best shown in Figure 6, which shows the windshield with the top wall removed, the first and second port openings 103, 104 may be arranged on the sidewall at an angle with respect to one another, in this example perpendicularly, on adjacent surfaces of the sidewall 1 . The respective axis of the first and second port openings 103 converge and meet to allow for the match 20 and match striker 19 to be brought into contact, within the enclosed space 100 to ignite the match. To facilitate the ignition, the length of the striker holder 18 may be selected accordingly to ensure contact between striker and match.

When the supply of gas is turned on and the gas emerges through the apertures 140 in the burner element 14, the match 20 can be held against the match striker 19, as guided by the port openings 103, 104, whilst the striker 19 is withdrawn back through the sidewall 1 of windshield 30, to ignite the gas. When the striker 19 is removed, the second port shutter 5 is moved in a clockwise direction to cover the second port opening 104. The lit match 20 is pushed into the space 100 enclosed by windshield 30 and the first port shutter 6 is moved in an anticlockwise direction, to cover the first port opening 103. Closing the first and second port shutters 6, 5 minimises the amount of wind, for example, that enters the space 100 and also prevents light generated from the burning fuel from escaping. The base light shield 1 1 , on which the burner attachment 13 and burner element 14 are supported, may also prevent wind from entering the space 100 and minimise light generated from the burning fuel from being seen from underneath the stove 30.

The first port opening 103 and a head 204 of the match 20 may have an engineering fit, e.g. a loose running clearance fit. The second port opening 104 and the striker holder 18 may also have an engineering fit, e.g. a loose running clearance fit. This may allow the match 20 and striker holder 18 to be guided by the first and second port openings 103, 104, respectively, which can help usability in harsh conditions, such as extreme cold, where a user’s dexterity may be compromised.

Turning now to Figure 7, there is shown an arrangement of the windshield where the plurality of legs 4 are adjustable between different angular positions with respect to the sidewall, to position the windshield between different height positions.

Each leg may be pronged in that it comprises a first arm 421 and a second arm 422 that are connected at a base 423. The first and second arms 421 , 424 is offset from the base 423 at an angle with respect to one another. The second arm 422 may be narrower than the first arm 421 such that it can be resiliently deflectable with respect to the first arm 421 . This may be facilitated by manufacturing the legs from spring steel. The first arm 421 has a first end distal to the base 423 that is pivotably connected to the sidewall 1 via an indexer 3 that is fixedly attached to the sidewall 1 (although in arrangements the leg may be attached directly to the sidewall 1 ). The second arm 422, meanwhile, has a free end 424 distal to the base 423 which is configured to be rotated within the same rotational plane as the first arm 421 . In the top illustration of Figure 7, the windshield 30 is in a stowed configuration, where the legs 4 are rotated to be adjacent with the sidewall 1 along their entire length.

In the middle illustration, the legs 4 are rotated to an extended position so that the second arm 422 of each leg 4 interacts with leg indexer 3 in a first stationary position. At the first stationary position, the legs 4 are in their most extended position, providing the windshield 30 with a high position off any surface it is situated on.

In particular, the free end 424, when rotated in an anti-clockwise direction, for example, may be brought (rotated) into contact with and engages a first lug 425 of the indexer 425 such that the leg, e.g. the first arm 421 , is held at a first stationary position that is at a first angle 710 with respect to a vertical direction (which is parallel with the sidewall 1 , in this example). The first lug 425 is arranged on the indexer 3 at a first circumferential position about the pivot connection 426 about which the leg 4 rotates. The lug is in the form of a ridge or notch on the surface of the indexer 3 that meets and engages the free end of the leg to prevent its tendency to rotate by a force due to the mass of the windshield under gravity.

In the bottom illustration, the legs 4 are extended so that the second arm 422 of each leg 4 interacts with indexer 3 in a second stationary position. This second position means that the legs 4 are in a less extended position, providing the windshield 30 with a lower position off any surface it is situated on. Each of the four legs 4 can be set in either of these two positions, so that the windshield 30 can be kept relatively level if it is situated on uneven ground.

The second arm 422, particularly the free end 424, is resiliently deflectable from the rotational plane of the first arm 421 (and the first lug) such that when the free end 424 is deflected away from the sidewall 1 and first lug (e.g. in the normal direction of the sidewall surface) it can be moved (rotated) further in the anti-clockwise direction. In particular, the free end 424 may be rotated anti-clockwise from the first lug 425 to a second lug 427 of the indexer 3, which is at a second circumferential position that is angularly displaced from the first lug 425 along the circumferential direction about the pivot connection 426, and also elevated from the first lug 425 in a direction away from the sidewall 1 (e.g. in the normal direction of the sidewall surface). When the free end 424 is brought into contact with and engages the second lug 427 of the indexer 425, the leg, e.g. the first arm 421 , is held at a second stationary position that is at a second angle 720 with respect to a vertical direction (parallel with the sidewall 1 , in this example).

The first and second angles 710, 720 are different to each other such that the windshield 30 may be positioned between two different height positions corresponding to the first and second stationary positions.

It will be appreciated that while the legs and lugs have been described above with respect to rotation in an anti-clockwise direction, it is equally possible for the legs to be configured to rotate in a clockwise direction to engage the first and second lugs in turn. Indeed, the legs of the windshield may be configured to rotate in different directions with respect to each other, to engage corresponding lugs.

With reference to Figures 1 and 8 to 10, there will now be described a spring lock mechanism 9 of the burner assembly 50, which allows the burner assembly 50 to be removably attached to the windshield 30. As best shown in Figures 1 and 8, the burner assembly 50 has a central longitudinal axis 501 along which the burner assembly 50 components are assembled.

The spring lock mechanism 9 is centred on the longitudinal axis 501 and is provided between the fuel supply attachment (gas diverter) 7 and the base light shield 1 1. The mechanism 9 is, in this example, in the form of a folded piece of sheet metal that includes a base 91 having a planar surface that is perpendicular to the longitudinal axis 501 and that includes a plurality of arms 93 arranged circumferentially about the longitudinal axis 501 of the burner assembly 50. Each arm 93 has been folded about a respective bending point 94 such that it extends out of plane from the planar surface of the base 91 and generally towards (but not necessarily parallel with) the longitudinal axis 501 . The planar surface of the base 91 may include a central hole 92 for receiving mixing tube 10 therethrough, which is itself snugly attached over a protruding portion of the gas diverter 7. Additionally, the arms 93 may have a longitudinal extent parallel to the longitudinal axis 501 such that they surround at least the mixing tube 10 and a portion of the burner attachment 13, when fully assembled. In this example, the arms 93 do not extend as far as the base light shield 1 1 of the burner assembly, such that the base light shield 1 1 , burner base 12, burner attachment 13 and burner element 14 positioned longitudinally forward of the arms 93 in the direction of gas flow.

Given that the arms 93 are folded from the planar surface of the base 91 , the arms 93 are deflectable about the bending point 94 in the radial direction, but provided with a spring force that biases the arms 93 radially outwards from the longitudinal axis 501 , e.g. substantially perpendicularly to the axis 501 . In this way, the arms may be considered to be resiliently deflectable. This may be facilitated by manufacturing the arms and/or base from spring steel.

On the radially outer surface of each arm 93 is at least one notch 95. The notch 95 may be substantially C-shaped in cross-section. The notches 95 of the arms 93 face radially outwards such that, when the burner assembly is received through aperture 21 1 on the bottom wall 21 , they can be brought into a facing arrangement with corresponding notches 96 on the rim 215 of the aperture 21 1 (i.e. flange 213) in bottom wall 21 of the windshield 30.

As best shown in Figures 9 and 10, the burner assembly 30 can be attached to or removed from the windshield 30 by applying a compressive force to the arms 93 of the spring lock mechanism 9, as shown by arrows 502 in Figure 9.

A compressive force can be applied to the arms 93 such that the arms 93 are moved radially inwards towards the central longitudinal axis of the burner assembly 50, against the inherent spring bias in the arms 93. In the compressed state, the radial extent of the burner assembly (including arms 93) is reduced to a point that it is smaller than the diameter of the aperture 21 1 in bottom wall 21 of the windshield 30. In this way, the burner assembly (with the gas hose 16 removed) can be moved freely through the aperture 21 1 , along an insertion/removal direction corresponding to the axis of the aperture 21 1 .

To attach the burner assembly 50, the assembly 50 is moved while in the compressed state to a position at which the notches 95 of the arms 93 are at the same position along the insertion direction as the corresponding notches 96 on the rim 215 of the aperture 21 1. At that position, the compressive force can be released such that the notches 95 move radially outwards (under the spring bias) to engage the corresponding notches 96 on the rim 215 of the aperture 21 1 . The notches 95 on each arm 93 correspond to respective notches 96 on the rim 215 of the aperture 21 1 in that they are of a similar size and are arranged perpendicularly to one another. For example a pair of corresponding notches 95, 96 may have the same C-shape in cross- section, but may be arranged perpendicularly with respect to one another so that they can engage each other. In this manner, the spring lock mechanism 9 (and burner assembly 50 generally) may be locked in both rotation and longitudinal translation, when in the engaged configuration.

To detach the burner assembly 50, the arms 93 are compressed as described above such that the assembly 50 can be moved along the removal direction 97, opposite the insertion direction (not shown), towards the top wall 2 of the windshield 30.

The burner element 14 and gas diverter 7 are at longitudinally opposite ends of the burner assembly 30, a first end corresponding to the burner element 14 and a second end corresponding to gas diverter 7. It will be appreciated that the burner assembly 50 is shown in Figure 1 in an inverted orientation where the direction of gas flow through from the gas diverter 7 to the burner element 14 is opposite to the direction from the bottom wall 21 to the top wall 2 of the windshield 30. Flowever, in use, the burner assembly will be oriented in an upright configuration such that the direction of gas flow from the gas diverter 7 to the burner element 14 is substantially the same direction as that from the bottom wall 21 to the top wall 2. In other words, the burner assembly 30 will be oriented in use such that the burner element 14 faces the aperture 200 in the planar surface 202 of the top wall 2.

The burner assembly 50 (with or without gas hose 16 or control module 17 connected thereto) can be attached to the windshield 30 by the spring lock 9 in either an upright configuration or an inverted orientation as described above with respect to Figure 1 . To avoid any parts of the burner assembly 50 protruding from the windshield 30 through the aperture 200 in the top wall 2 while in the inverted configuration, the depth of the windshield 30 to the aperture 21 1 on the bottom wall 21 , particularly the flange 213 that defines the rim of the aperture 21 1 , is selected such that it is larger than a longitudinal extent of the burner assembly between the second longitudinal end (corresponding to the gas diverter 7) and the notches 95 on the resiliently deflectable arms 93. The height 214 of the radially inner surface 212 of the reservoir 210 may also be selected to match the longitudinal extent of the burner assembly 50 between the notches 95 and the burner element 14. In this way, the radially inner space between the radially inner surface 212 is suitably long enough to receive the longitudinal extent of the burner assembly 50 between the notches 95 and the burner element 14, without any part of the burner assembly 50 protruding further outwards than the bottommost surface 98 of the bottom wall 21.

It will be understood that the invention is not limited to the embodiments above- described and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the invention extends to and includes all combinations and sub-combinations of one or more features described herein. For example, the windshield 30 can have a generally circular shape of form, rather than rectangular form described above. Further, a person skilled in the art will appreciate that the top wall 2, legs 4, striker port shutter 5 and match port shutter 6 can also be configured for any alterative windshield configuration.