US20100192933A1

US20100192933A1 - Alcohol stove and method for igniting an alcohol stove

Info

Publication number: US20100192933A1
Application number: US12/669,247
Authority: US
Inventors: Hans-Olof Andersson
Original assignee: Dometic Sweden AB
Current assignee: Dometic Sweden AB
Priority date: 2007-07-20
Filing date: 2008-07-16
Publication date: 2010-08-05
Also published as: EP2227658A1; WO2009014487A1; EP2227658A4; SE0701756L; SE531070C2

Abstract

The present invention relates to an alcohol stove comprising a casing (10), whereby the housing comprises one or several fire hearths (17) and encases a fuel container (22) and a burner arrangement (20), wherein a heating wire (101) is arranged above the opening (25) of the fuel container (22) and that the heating wire (101) is connected to a connectable electrical power source, which when connected causes the heating wire (101) to heat up so that the heating wire (101) by heat radiation evaporates the fuel in the fuel container (22) such that the alcohol stove is ignited by the fuel fume vapours being ignited as they pass the heating wire (101).

Description

AREA OF THE INVENTION

The present invention is generally directed to alcohol stoves and more particularly to electric ignition of such an alcohol stove.

BACKGROUND OF THE INVENTION

Alcohol stoves for non-pressure burning are previously known in the art. A common principle for these apparatuses is that the fuel is stored in a container, which is filled with a fuel absorbing porous substance. The container comprises an upper opening from which the fuel evaporates during burning, wherein a cooking-utensil is placed above the opening. An example of such an alcohol stove is described in EP 294426. Another example of such an alcohol stove is described in the applicant's own patent document SE 523 105.
When the user wants to ignite his/her alcohol stove, he or she pushes to the side a disc or plate covering the opening of the fuel container. Thereafter, the alcohol stove is ignited by using a match or the like. This method of igniting comprises several disadvantages. For example, during windy circumstances it can be hard and awkward to manage to keep the match burning until it has reached the opening of the fuel container. Moreover, the fuel container is disposed a bit underneath the cooking-utensil stand, hence it is necessary to put the match or the lighter a bit downward in order to ignite the alcohol stove. This method of ignition also requires the user of the alcohol stove to have matches, a lighter or the like at hand if he/she wishes to use the alcohol stove. Moreover, all handling of matches and the like presents a safety risk.

SUMMARY OF THE INVENTION

The present invention provides a solution the problems described above and gives a substantial simplification and improvement of the use of alcohol stoves. An alcohol stove comprises, among other things, a fuel container containing fuel. By arranging an electric ignition device above the fuel container, an alcohol stove that is both safe and easy to use is obtained. The electric ignition device comprises an electric switch that is connected to a built in battery in the alcohol stove or to an external power source and to an electrically conducting heating wire. The electric ignition device works such that, when the switch is closed, the heating wire is heated up such that it in turn radiates heat down into the opening if the fuel container. This heat radiation leads to the fuel or alcohol in the container to heat up and start evaporating. As these fume vapour rises, they pass the heating wire which then ignites the fume vapour, which leads to the ignition of the alcohol stove.
According to an embodiment of the present invention, the heating wire is arranged at a distance of 1 to 10 mm above the opening of the fuel container, preferably approximately 5 mm. This gives a good and efficient heat radiation down into the fuel container for heating up and evaporating the fuel in the fuel container so that the fume vapours are easily ignited as they pass the heating wire and thereby ignite the alcohol stove.
According to an embodiment of the present invention, the heating wire is composed of a ceramic composite material, metal or any other electrically heatable material. Preferably, a ceramic composite material is used as this both has good electrically heating capabilities and is also heat durable. The heating wire is subjected to high temperatures as it is constantly disposed in the flame when the alcohol stove is used, which demands for the heating wire to be able to withstand high temperatures for a very long time with out being damaged or destroyed.
According to an embodiment of the present invention, the electric switch is composed by a micro switch that is closed when a knob, which is arranged in the housing of the alcohol stove, is turned to the maximum and remains closed as long as the knob is kept in this position and that is opened as the knob is released. This provides a simple, robust and inexpensive solution for obtaining an electric ignition of the alcohol stove. The user simply turns the knob to the maximum and holds it in this position until the alcohol stove is ignited, whereupon the user releases the knob causing the voltage to the heating wire to be disrupted.
According to an embodiment of the present invention, the electric ignition device comprises an electric circuit, which comprises logic with timing capabilities so that the electric circuit is automatically activated when the knob is turned and simultaneously a countdown of a predetermined length is initiated. When the countdown expires, the voltage to the heating wire is disrupted. This embodiment enables the user to not having to hold the knob in the maximum turned position, which provides a more automated alcohol stove.
The invention also relates to a method for igniting an alcohol stove. With the method according to the invention, corresponding objects and advantages are achieved as described above. Further objects and advantages of the invention will be evident from the following detailed description of the invention and the patent claims.
The invention will now be described by an exemplary embodiment and with reference to the accompanying drawings.

SHORT DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plan view of an alcohol stove viewed from above, at which the present invention can be implemented.

FIG. 2 shows a corresponding plan view from underneath.

FIG. 3 is a cross section along line in FIG. 1.

FIG. 4 shows, in a bigger scale, a cross section through the stove and the fuel container, but with another type of cooking-utensil stand than shown in FIG. 3.

FIG. 5 shows an electric ignition device in the form of a heating wire arranged above a fuel container.

FIG. 6 shows a cross section viewed from the side of an alcohol stove.

FIG. 7 shows an alcohol stove according to the present invention.

FIG. 8 illustrates a preferred embodiment of the device of the electric heating wire.

DETAILED DESCRIPTION OF THE INVENTION

In the following, firstly an alcohol stove is described at which the present invention can be implemented. It shall be noted that the electric ignition device according to the invention can be used with a plurality of different types of alcohol stoves and is not limited to the one hereinafter described. The exemplified alcohol stove in FIG. 1 comprises a box shaped frame 10 without a bottom part. This frame is made in one piece, preferably by deep drawing and consists, for example, by stainless steel in order to withstand corrosion as much as possible. The frame rests at its lower part on a corbelled-out foot section 11 and displays a circumferential substantially vertical wall 12 that transitions into a horizontal hearth 13, wherein the hearth comprises a raised edge section 14 and inside this, an existing bottom section 15. The gables of the vertical wall 12 have a number of small openings 12 a, see FIG. 3, through which combustion air flows into the frame. The bottom section transitions in turn into two step-shaped circular raises that each displays a first ring-shaped ledge 16 and a second central ledge 17. The rings-shaped ledge 16 has a number of relatively small perforations 18, intended to limit the heat transfer between the central ledge 17 and the other parts of the frame, while the central ledge 17 displays a number of circular openings 19 that form a flame spreader for a burner 20 placed underneath the hearth. The showed embodiment thus displays a two-flame alcohol stove, but the invention is of course intended to be applied at alcohol stoves with one or more than two flames.
Reference is now made also to FIG. 2-4. The frame 10 incorporates a substantially U-shaped heat-shielding plate 21 that is turned upside down and that is fixed at the foot section 11 and that partly surrounds two cylindrical fuel containers 22. It shall be noted in this context that although the illustrated alcohol stove comprises two cylindrical fuel containers, these may of course be replaced by a single container of arbitrary shape or several such containers. The heat-shielding plate 21 that prevents radiated heat from the hearth to reach the fuel container (which could cause the fuel in the fuel container to boil) extends along the major portion of the frame in the longitudinal direction and exhibits two circular openings 23 that are coaxially arranged with regard to the central ledges 17 and that surrounds a, through the opening protruding, ring-shaped edge section 24 of each of the fuel containers 22, wherein the edge section 24 in turn surrounds a central opening 25 of the fuel container. Each of the fuel containers is adjusted with regard to the openings 23 by means of a number of guiding elements 26 that are punched out in the heat-shielding plate, wherein these guiding elements are somewhat tilted towards a vertical plane. Each of the fuel containers 22 are supported and fixed to the frame by means of a couple of locking plates 27, which are arranged to be turnable around vertically arranged axis 28, wherein the locking plates are arranged somewhat flexibly in the vertical direction by means of a elastic washer 29 or similar. The locking plates 27 are retained in their locking positions by means of grinders 30, see FIG. 2, arranged on the heat-shielding plate.
The heat-shielding plate 21 also supports two vertical burner pipes 32, each of the burner pipes is connected to a ring-shaped footplate 33 with a number of downwards projecting distance elements 34, which are fixated in immediate connection to the circumference of the openings 23. Further, the heat-shielding plate 21 supports two arms 35, which are rotatably attached around vertical axis 36, wherein one end of each arm 35 extends through a respective slot 37 arranged in the vertical wall 12 of the frame, wherein the other end of the arms extends between two of the distance elements 34 and each supports an extinguishing plate or control plate 38. The control plate 38 is circular and is arranged to expose, alternatively totally or partly cover the opening 25 of the fuel container 22 by manual actuation of the arm 35 from the outside of the frame. The control plate 38 functions such that it to a major or smaller degree, depending upon its position, hinders the heat radiation from the flame to reach the opening 25 and thereby the surface where the fuel evaporates, which results in that the size of the flame becomes a direct function of the size of the exposed surface, which in turn results in that the size of the flame can be regulated.
The fuel container 22 comprises a circular container with a bottom 39, a side wall section 40 and a top part 41, wherein the top part surrounds the opening 25 of the fuel container and transitions into the ring-shaped edge section 24. The bottom 39 comprises a central inwards projecting protrusion 42 and the top part 41 has a circumferential flange-like upwards-projecting edge section 43 that connects the top part 41 with the sidewall section 40. The fuel container 22 contains a porous liquid absorbing substance, which consists of a cylindrical part 44 and, placed outside of this, a ring-shaped part 45, wherein the substance partly is covered by a net 46 that prevents the substance from falling out through the opening and which is pulled in under the top part. At the mounting of the fuel container, the protrusion 42 will push the central part upwards in relation to the ring-shaped part 45 such that the central part 44 is brought to be aligned against the net 46, whereby an evaporation surface is formed in connection to the upper part of the fuel container for the existing fuel in the fuel container.
At the alcohol stove that is depicted in FIGS. 1-4, two cooking-utility stands are provided on the top of the hearth. Each of the cooking-utility stands comprises four band-shaped sections 48 that are fixed to each other to form a ring-shaped structure with a tubular circular windshield part 49, a number if inwards projecting parts 50 and a number of outwards projecting parts 51, wherein the outwards projecting parts have a longer vertical propagation than the windshield part such that a lower opening 52 is formed, see FIG. 3, between the bottom part 15 of the hearth and the windshield part 49 and an upper opening 53 between the windshield part and a cooking utensil that is resting on the cooking-utensil stand. The lower edges of the inwards projecting parts 50 and the outwards projecting part 51 are designed such that the shape of the cooking-utensil stand corresponds to the shape of the hearth, whereby the cooking-utensil stand easily can be centred around the central ledge 17.
In the alcohol stove that is showed in FIG. 4, the cooking-utensil stand comprises four radial plates 54 with a step-shaped lower edge section 55, which is adapted to the shape of the hearth, wherein the plates are fixed to a ring 56 that surrounds the central ledge.
It is also possible to replace the locking plates 27 with one or several through-shaped collection boxes, which are placed underneath the fuel containers so that the boxes collect fuel that may leak from the fuel container while the boxes are rotatably hanging in the frame and can be locked in a horizontal position and thereby press the fuel containers against the heat-shielding plate.
According to the present invention and with reference to FIGS. 5-8, an electric ignition device comprising a heating wire 101, an electric switch 107, for example a micro switch 107 and an electrical power source is provided. The electric ignition device constitutes a closed electric circuit comprising the connected heating wire 101, the electric switch 107 and the power source. The function of the heating wire 101 is that when it is supplied with voltage, it will heat up in order to radiate heat. The heating wire 101 can be made of a ceramic composite material, metal or other electrically conducting/heatable material. In connection with the opening 25 of the fuel container, a fastening arrangement is provided, with which the heating wire can be kept at an appropriate position above the opening 25. The fastening arrangement can, for example, consist of one or more holders 100 a, 100 b as is shown in FIG. 5. In another embodiment, showed in FIG. 8, the fastening arrangement comprises a holder 100 c arranged in the footplate 33 of the vertical burner pipe 32. With reference to FIG. 5, these holders are arranged at said holders 100 a, 100 b so that the electrically conducting/heatable heating wire 101 extends over and above the opening 25 of the fuel container. The holders 100 a, 100 b are designed such that the vertical distance between the opening 25 of the fuel container or the corresponding control plate 38 and the electrically conducting/heatable heating wire 101 is in the range of 1-10 mm, preferable close to 5 mm. The heating wire 101 is in a preferred embodiment U-shaped, but other embodiments are possible, such as a wire all across the opening 25 or in different shapes, for example S-shaped, pleated and so on.
The electrically conducting heating wire 101 is connected to an electric switch 107 and a power source (not shown). The power source is typically 12 Volts but other voltages are possible and it can comprise a built-in battery or it can comprise an external power source to which the alcohol stove can be connected. In is simplest form, the electric switch 107 comprises a micro switch 107. The electric switch functions such that when it is closed, voltage is supplied to the heating wire, whereby the heating wire is heated.
The electric switch 107 is preferably arranged at the arm 35 that controls the movement of the control plate 38 over the opening 25 of the fuel container 22 or in connection to a knob 105 (will be described below) that controls the movement of the arm 35.
In the preferred embodiment that is shown in FIG. 8, the heating wire is arranged in the footplate 33 of the vertical burner pipe 32. The footplate 33 is designed with a recess 100 c, which comprises said holder, in the horizontal part of the footplate 33 where the heating wire can be inserted and kept in place so that the heating wire extends above the opening 25 of the fuel container 22 and at an appropriate distance in the vertical direction above the opening 25. The footplate is arranged at a certain distance above the fuel container 22 by the distance elements 34, which are vertically upstanding from the heat-shielding plate 21. The distance elements 34 are arranged in this embodiment such that the heating wire 101 is positioned at an appropriate distance above the opening 25 of the fuel container 22.
In the embodiment shown in FIG. 5, the fastening arrangement can comprise one or several separate holders. Arranged such that the heating wire can be placed directly below the footplate 33 such that the distance in the vertical direction between the heating wire 101 and the opening 25 is within the range 1-10 mm. In this embodiment, also the heating wire is provided with heat-shielding insulation of the part that is placed along the underside of the footplate 33, as this part will be subjected to heat radiation when the alcohol stove is in use. The holder 100 a or the holders 100 a, b are in this embodiment preferably arranged on the heat-shielding plate 21. The holders 100 a, b can also be arranged in one or several of the vertical distance elements 34.
When voltage is being supplied the heating wire by the electric switch 107, the heating wire is heated. In connection with supplying voltage to the heating wire, the control plate 38 is opened to its maximum so that the opening 25 of the fuel container 22 is entirely exposed. The heat from the heating wire radiates down towards the fuel/alcohol in the fuel container, which results in heating of the fuel, whereby it starts to evaporate. As the fuel evaporates, the fume vapour rises and passes the heating wire, which then ignites the fuel fume vapour. This results in that the existing fuel in the fuel container 22 ignites and a flame is formed that extends from the net 46 in the opening 25, up through the burner pipe 32 and through the openings of the flame spreader, where it thus is spread in a number of smaller flames that spread along the underside of the cooking-utensil. The size of the flames can thereafter be controlled by means of the control plate 38 by actuating the arm 35 and the flames can be extinguished after use, by bringing the control plate to completely cover the opening 25 of the fuel container 22.
According to an alternative embodiment, which is not shown in any figure, a reflector plate can be arranged vertically above the heating wire to reflect down more heat towards the fuel in the fuel container 22. Such a reflector plate may, in such a case be designed in several different ways. It may completely or partially cover the heating wire and if may be formed of a solid piece or with holes, slits or other openings in the reflector plate to allow for passage of air and/or fuel fume vapours.
The powering of the heating wire can be activated in different ways, more or less automatically or entirely manually. The movement of the control plate 38 across the opening 25 is actuated by the arm 35. The arm in turn, may preferably be actuated by the control knob 105 arranged on the housing 10 of the alcohol stove, for example a knob 105 of conventional sort. This is illustrated in FIG. 6. In a preferred embodiment, the knob 105 is designed as follows. Firstly, it is turned maximally in order for the control plate 38 to completely expose the opening 25. Further, the knob 105 is provided with a spring arrangement such that the last part of the turning of the knob 105 causes the spring arrangement to be a bit stressed and simultaneously the switch 107 is closed to supply voltage to the heating wire 101. The user keeps the knob 105 turned until he or she sees that the alcohol stove is ignited and then releases the knob 105, which then springs back just a little without affecting or diminishing the strength of the flame. As the knob 105 springs back, the switch 107 opens to no longer supply any voltage to the heating wire 101. The opening 25 is still maximally exposed and the user can regulate the heat, that is the size of the flame, by turning the knob 105, which then will push the control plate 38 across the opening 25. To extinguish the flame and thereby switch off the alcohol stove, the knob 105 is turned to its original position, which results in the control plate 38 entirely covering the opening 25 of the fuel container 22.
Alternatively, the electric ignition device may also be designed to comprise further components. For example, components can be added in order to implement a function, which activates the electric ignition device as the knob 105 is turned and then supplies a voltage to the heating wire 101. Simultaneously, a countdown procedure is initiated having a predetermined length. When the countdown ends, the voltage to the heating wire 101 is automatically disrupted so that there will be no risk for the heating wire to be constantly supplied with a voltage, which could lead to it being destroyed or damaged. As the voltage is disrupted, the heating of the heating wire 101 is terminated. In the case that the power source is a battery, it is also preferable not to supply voltage to the heating wire 101 more than necessary in order to maximise the service life of the battery. In this embodiment, the predetermined time that is allowed to pass before the circuit is opened should be chosen such that the alcohol stove most probably will be ignited.
Another alternative to activate the heating wire is that the above-mentioned knob 105, only controls the control plate 38. A separate activation arrangement such as a button, a knob or similar 106 is arranged on the alcohol stove that will close the switch 107, which then will supply voltage to the heating wire as the button 106 is pressed or turned. This is illustrated in FIG. 7. In order to ignite the alcohol stove in such an embodiment, the first knob 105, which will open the opening 25, must first be turned. Thereafter, the button 106 is pressed until the alcohol stove is ignited, or when the activation arrangement is a knob 106 the knob 106 is turned until the alcohol stove is ignited. As the button 106 is released, the switch disrupts the voltage to the heating wire 101.
Yet another alternative is that the first knob 105 is both turned and pressed. The pressing of the knob will close the micro switch 107 and activate the supply of voltage to the heating wire 101, and when the knob 105 is released so that it can spring back out, the micro switch 107 disrupts the voltage to the heating wire 101.
The heating wire 101 is chosen such that it possesses a required or appropriate resistance so that when voltage is supplied via the micro switch 107, it will heat up and radiate enough heat towards the fuel in the fuel container 22 in order to heat up, evaporate and via the fume vapours ignite the fuel in the fuel container. Also the distance from the heating wire to the fuel is of importance in order to radiate enough heat in order to heat up, evaporate and via the fume vapours ignite the fuel in the fuel container.

Claims

1. An alcohol stove comprising a housing (10), wherein the housing comprises at least one fire hearth (17) and encases a fuel container (22) and a burner arrangement (20) characterized in an electric ignition device, which is connectable to an electrical power source, wherein said ignition device comprises a heating wire (101) and a switch (107) arranged to be enabled to be connected together to constitute a closed electric circuit, wherein the heating wire (101) is arranged above an opening (25) of the fuel container (22) and connected to said power source via said switch (107), wherein the heating wire (101) is arranged to be heatable in order to, by heat radiation, evaporate fuel in the fuel container (22) such that said alcohol stove is ignited by ignition of fuel fume vapours as they pass the heating wire (101).

2. An alcohol stove according to claim 1, characterized in that the heating wire (101) is arranged 1-10 mm above the opening of the fuel container (22).

3. An alcohol stove according to claim 1, characterized in that the heating wire (101) is arranged approximately 5 mm above the opening of the fuel container (22).

4. An alcohol stove according to any of the preceding claims, characterized in that said power source consists of a built-in battery.

5. An alcohol stove according to any of claims 1-3, characterized in that said power source consists of an external power source to which the alcohol stove can be connected.

6. An alcohol stove according to any of the preceding claims, characterized in that heating wire (101) is made from any of a ceramic composite material, metal or other electrically heatable material.

7. An alcohol stove according to any of the preceding claims, characterized in that said switch (107) consists of a micro switch (107) that is closed automatically when a knob (105) arranged in said housing (10) is turned maximally, remains closed as long as the knob (105) is kept in this position and opens when the knob (105) is released.

8. An alcohol stove according to any of claims 1-6, characterized in that the electric ignition device further comprises an electric circuit comprising logic with timing capabilities, wherein said electric circuit is automatically activated when a knob (105), arranged in said housing (10), is turned and initiates simultaneously a countdown of a predetermined length and supplies voltage to the heating wire (101), remains active as long as the countdown proceeds and disrupts the supply of voltage to the heating wire (101) as the countdown has been completed.

9. An alcohol stove according to any of claims 1-6, characterized in that said switch (107) consists of a micro switch (107) that is arranged to be closed automatically when an activation arrangement, such as a knob (106) or a button (106) arranged in said housing (10), is activated, remains closed as long as the knob (106) is kept in its turned position or the button (106) is being pressed and opens when the knob (106) is turned back or the button (106) is released.

10. Method for igniting an alcohol stove comprising a housing (10), wherein the housing comprises at least one fire hearth (17) and encases a fuel container (22) and a burner arrangement (20) characterized in connecting a heating wire (101) arranged above the opening (25) of the fuel container (22) via a switch (107) to a power source that when connected brings the heating wire (101) to heat up so that the heating wire (101) by heat radiation evaporates the fuel in the fuel container (22) so that the alcohol stove is ignited by the fuel fume vapours being ignited as they pass the heating wire (101).