WO2009071100A1

WO2009071100A1 - Wick for a fuel burner

Info

Publication number: WO2009071100A1
Application number: PCT/DK2008/050298
Authority: WO
Inventors: Lone Ogaard Rasmussen; Henrik Casper
Original assignee: Ideas Denmark A/S
Priority date: 2007-12-06
Filing date: 2008-12-05
Publication date: 2009-06-11

Abstract

The present invention relates to a wick (4) for a fuel burner (1), said wick (4) being adapted to draw up fuel (6) by utilizing capillarity from a reservoir (2) to a flame location end (7) at which the drawn-up fuel (6) is intended for being burnt. The wick (4) comprises one or more inner channels (8) extending from a suction end (5) of the wick (4) for suction of the fuel (6) from the reservoir (2), to the flame location end (7) of the wick (4) for producing a flame of the drawn-up fuel (6), said one or more inner channels (8) each having a substantially tubular- shaped inner surface (9). The invention further relates to a fuel burner (1) comprising a fuel reservoir (2) and a wick (4) as described, the wick (4) being arranged to draw up fuel (6) from the fuel reservoir (2).

Description

WICK FOR A FUEL BURNER

FIELD OF THE INVENTION

The present invention relates to wicks for fuel burners and in particular to wicks in which the fuel is drawn up from a reservoir by utilizing capillarity.

BACKGROUND OF THE INVENTION

In a number of fuel burner applications, a wick is used to draw up the fuel to be burned from a reservoir typically contained within the burner. Such applications include cigarette lighters, fire-lighting devices, torches, and oil lamps. Some of the materials used for wicks degrade during use and they also often produce undesired soot, especially if they are too long. The soot may lead to miscolouring of e.g. a wall close to which an oil lamp is placed.

It is known from EP 0 978 686 to use wicks made from a porous ceramic fibre material which draw up the fuel by utilizing capillarity. The reference discloses a wick having a tip flame-producing section and a draw-up section which is placed in a fuel reservoir of e.g. a cigarette lighter. A part or all of the side surfaces of the flame-producing section of the wick is provided with a skin layer for suppressing volatization of liquid fuel from the side surfaces. Hereby it is possible to obtain a more narrow flame than what is possible with a porous wick without such a skin layer.

OBJECT OF THE INVENTION It is an object of the present invention to provide a wick by use of which a fuel can burn without producing soot.

It is another object of the present invention to provide a wick which does not decompose or degrade during use.

It is a further object of embodiments of the present invention to provide a wick for drawing up fuel by capillarity by which wick a narrow flame can be obtained without the need to add a skin layer having different volatizing properties than the rest of the wick. It is a further object of the present invention to provide an alternative to the prior art.

SUMMARY OF THE INVENTION Thus, the above described object and several other objects are intended to be obtained in a first aspect of the invention by providing a wick for a fuel burner, said wick being adapted to draw up fuel by utilizing capillarity from a reservoir to a flame location end at which the drawn-up fuel is intended for being burnt, said wick comprising one or more inner channels extending from a suction end of the wick for suction of the fuel from the reservoir, to the flame location end of the wick for producing a flame of the drawn-up fuel, said one or more inner channels each having a substantially tubular-shaped inner surface.

By tubular-shaped is preferably meant that the cross section of a channel is substantially constant along the whole length of the wick. It is however also possible within the scope of the invention that the cross section changes, e.g. by a decrease or increase in the size at one or more positions along the length.

By fuel is preferably meant a liquid fuel.

In some embodiments of the invention, each of the one or more channels may be a slit. Such a slit may extend from a longitudinal axis of the wick and in a direction perpendicular to the longitudinal axis in any cross section of the wick.

A wick comprising slits may be assembled from at least two wick parts so that slits are established between facing surfaces of the wick parts. Hereby it may be easier to obtain very small dimensions of the slits from wick parts manufactured without channels. This may result in a more simple manufacturing process.

The thickness of the one or more slits may between 0.05 and 2 mm, such as between 0.05 and 0.5 mm, between 0.5 and 1 mm or between 1 and 2 mm. The size is chosen so that a stable flame of a desired size is obtained and so that the drawn up fuel corresponds to an appropriate burning rate. A wick comprising one or more slits may further comprise an elongated cavity along the longitudinal axis of the wick. By elongated cavity is preferably meant a channel extending from the suction end of the wick to the flame location end. Hereby the demands on the dimensional tolerances in the manufacturing of the wick parts may be lowered. Furthermore an additional fibrous wick may be arranged in the cavity if desired.

In alternative embodiments of the invention, at least some of the channels may have a circular or oval cross section. In other alternative embodiments, at least some of the channels may have a polygonal cross section, such as a quadratic cross section. In other alternative embodiments, at least some of the channels may have an annular cross section, preferably a circular or oval cross section. The channels may also have an elongate cross sectional shape and be arranged to extend radially from an axis of symmetry of the wick. Such channels may e.g. be the slit-shaped channels described above.

In some embodiments of the invention, all of the channels have substantially the same cross sectional shape and size. In alternative embodiments the channels may constitute at least two sets of channels, and the channels in each set of channels may have substantially the same shape and size, which differs from either/both the shape and/or size of channels in the other one or more sets of channels. The possible combinations include a combination of two or more of the types described above. It may e.g. be possible to combine slit-shaped channels with channels having a circular cross section.

The channels may be arranged equidistant from an axis of symmetry of the wick and with a regular angular distance between adjacent channels. In embodiments comprising sets of channels, the channels in each set of channels may be arranged equidistant from an axis of symmetry of the wick and with a regular angular distance between adjacent channels. Such a symmetric arrangement may result in a symmetric flame.

The choice of size, shape and arrangement of the inner channels may depend both on the manufacturing method used and on the burning characteristics of a flame burning at the flame location end of the wick. Such burning characteristics, including e.g. the flame size and shape, may be determined by experimentation, by computer simulations or by any other appropriate method known to a person skilled in the art.

A wick according to the present invention may be made from at least one tubular- shaped rod and one or more massive or hollow other rods, wherein at least one tubular-shaped rod encircles the one or more other rods, and wherein at least one channel is formed between the rods. Hereby it may be possible to assemble a wick for a specific purpose from a range of pre-manufactured rods. The tubular shaped rod(s) encircling the one or more rods may have any appropriate cross sectional shape and size.

In any of the embodiments described above, the wick may comprise at least 10 inner channels, such as 10-20 inner channels, or 20-30 inner channels, or 30-40 inner channels. It is however also possible within the scope of the invention that the wick comprises only one channel or a few channels, such as 2-5 or 6-9 channels. It is furthermore possible to have a larger number of inner channels, such as up to 100 channels. The number and size of the channels may depend on the actual fuel used and on the desired flame size and shape.

In some embodiments of the invention, the wick may comprise a circumferential wall and a lid together at least partly forming an enclosure encapsulating a fibrous material adapted to draw up the fuel, wherein the lid may comprise at least one through-going hole through which fuel can be drawn from the fibrous material to the flame locating end. The size of the at least one hole and the thickness of the lid may preferably be so that the fibrous material is protected from burning or decomposing when the wick is in use. In such embodiments the suction end of the wick does not necessarily extend to the fuel reservoir, since the fuel may be drawn from the reservoir and to the suction end of the wick by the fibrous material extending to beyond the suction end and into the fuel reservoir.

Such a fibrous material may be selected from : glass, ceramic, cotton, and carbon.

The lid may comprise at least 10 holes, such 10 to 100 holes. Lids having one or only a few holes are also possible within the scope of the invention. An advantage of an embodiment comprising a lid and a fibrous material as described above may be that it is possible to change the lid and/or the fibrous material to suit a given type of fuel, a desired flame shape or flame size. However, the circumferential wall and the lid may also be a non-separable unit.

A wick according to the present invention may be made from a ceramic material, such as e.g. aluminium oxide or titanium oxide. It may alternatively be made from other types of materials, such as metal, stone, or polymer, or from a combination of two or more materials. The wick may e.g. be produced by rod extrusion or another process by which a product with a substantially constant cross section comprising inner channels as described above can be produced.

A second aspect of the invention relates to a fuel burner comprising a fuel reservoir and a wick as described above, the wick being arranged to draw up fuel from the fuel reservoir.

The fuel burner may further comprise a support member at least partly surrounding at least a part of the length of the wick and having an inner cylindrical surface corresponding to an outer surface of the wick. This may be desired to ensure a stable and secure fastening of the wick in the fuel burner.

In some fuel burners according to the second aspect of the invention, the flame location end of the wick extends beyond the support member. The flame location end may alternatively be substantially adjacent to an outer surface of the support member.

A fuel burner according to the second aspect of the invention may be an oil lamp for indoor and/or for outdoor use. The fuel burner may alternatively be used for e.g. cigarette lighters, fire-lighting devices, or torches.

The first and second aspect of the present invention may each be combined. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE FIGURES

The wick according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

Figure 1 shows schematically a cross sectional view of an embodiment of fuel burner according to the present invention,

Figure 2 shows schematically a top view of a wick having channels with a circular cross section,

Figure 3 shows schematically a top view of a wick having two sets of channels with different size,

Figure 4 shows schematically a top view of a wick having channels with annular cross section,

Figure 5 shows schematically a top view of a wick being made from hollow rods encircled by a tubular-shaped rod forming a shell member surrounding the other rods,

Figure 6 shows schematically a three-dimensional partial cross sectional view of a a support member partly surrounding the wick,

Figure 7 shows schematically a three-dimensional view of a wick comprising slits for drawing up the fuel; the wick is shown seen from partly from above,

Figure 8 shows schematically a cross sectional side view of a wick comprising a circumferential wall enclosing a cavity with a material which draws up fuel,

Figure 9 shows schematically a wick corresponding to the one shown in figure 8 except that the wick is shorter and the fibrous material extends beyond the suction end of the wick, Figure 10 shows schematically a cross sectional view of the upper part of the wick in figures 8 and 9,

and

Figure 11 shows schematically a top view of a lid of the wick shown in figures 8 and 9.

DETAILED DESCRIPTION OF AN EMBODIMENT Figure 1 shows schematically a cross sectional view of a fuel burner 1 according to the present invention. The burner 1 is shown to comprise a separate fuel reservoir 2 placed inside an outer housing 3. In an alternative embodiment (not shown), the lower part of the outer housing constitutes the fuel reservoir. The wick 4 has a suction end 5 placed in the fuel 6 and a flame location end 7. The wick 4 comprises one or more inner channels 8 extending from the suction end 5 of the wick 4 to the flame location end 7 of the wick 4. Only one channel is shown in the figure for clarity reasons. The fuel 6 is drawn-up by capillarity through the inner channels 8 which have a substantially tubular-shaped inner surface 9. By tubular- shaped is preferably meant that the cross section of a channel 8 is substantially constant along the whole length of the wick 4. It is however also possible within the scope of the invention that the cross section changes, e.g. by an abrupt decrease or increase in the size, at one or more positions along the length. The fuel burner 1 in figure 1 is shown with an open upper end. Other embodiments have a closed upper end.

Figure 2 shows schematically a top view of a wick 4 having channels 8 with a circular cross section. The size of the channels 8 are shown as being the same for all the channels 8, but the wick 4 may alternatively have two or more sets of channels with different sizes. An example of such an embodiment is shown in figure 3, where channels from the two sets are labelled 8a and 8b, respectively. In figures 2 the channels 8 all are arranged equidistant from an axis of symmetry of the wick 4 and with a regular angular distance between adjacent channels 8. In figure 3, the channels 8 in each set are arranged equidistant from an axis of symmetry of the wick 4 and with a regular angular distance between adjacent channels 8. Hereby it may be easiest to obtain a symmetrical flame is desired. However, embodiments without such a regular cross sectional pattern are also possible within the scope of the invention. Figure 4 shows schematically a top view of another embodiment of a wick 4 in which the channels 8 have an annular cross section. The choice of arrangement of the channels 8 may depend both on factors related to the manufacturing process and to factors related to the burning characteristics of the flame. For some applications a symmetric and stable flame is desired, whereas for other application a more flickering appearance is desired. The later may e.g. be the case for torches. The actual dimensions of the channels 8 in relation to the outer dimension of the wick 4 may be significantly smaller than what is shown schematically in the figures. The actual dimensions are chosen so that it is ensured that the wick 4 does not burn the fuel 6 faster than it is drawn up and so that only an appropriate amount of fuel 6 is used.

The wicks 4 shown in figures 2-4 may e.g. be made by extrusion of the full cross section in one extrusion process. A typical material may be ceramics which does not decompose, burn, or change appearance at the actual temperatures. An alternative thereto is to assemble the wick 4 from a number of rods 10 which may also be made from extruded ceramics. An example of such an assembly is shown schematically in figure 5 which shows a top view of a wick 4 being made from hollow rods 10 assembled by a tubular-shaped rod forming a shell 11 surrounding the other rods 10. The rods 10 may be identical or they may differ. Such an assembly results in additional channels 12 being formed, and depending on the size and arrangement of the rods 10, these additional channels 12 may or may not assist in the drawing-up of fuel by capillarity. Alternatively the rods 10 can be assembled by straps (not shown) or other holding means not covering the full length of the wick 4. This will result in a different appearance of the wick 4 which may be insignificant or desirable for decorative purposes.

Figure 6 shows a three-dimensional partial cross sectional view of a support member 13 partly surrounding the wick 4. This support member 13 may be the only means used to hold the wick 4 in place in a corresponding hole in a fuel burner, but it may also be used in combination with a support member (not shown) placed e.g. close to, such as directly on, the bottom surface of the fuel reservoir 2. Other ways of holding the wick in place are also possible within the scope of the invention. Figure 7 shows schematically an alternative embodiment of a wick 4. It comprises a number of slits 14 extending from the fuel reservoir 2 to the flame location end 7. The slits 14 may e.g. be established as opposite side surfaces of wick parts 15 spaced apart by one or more inserts (not shown) or by protrusions (not shown) on at least some of the wick parts 15. In such an embodiment the slits 14 extend radially from a longitudinal axis of the wick 4. Alternatively a wick 4 comprising such slits 14 may be manufactured as one piece with the slits 14 extending radially but not all the way from the axis to the circumference of the wick 4. A wick 4 with slits 14 may further comprise a central hole 16 along the whole length. Hereby it may be easier to assemble a wick 4 from more wick parts 15 without the need for very tight dimensional tolerances. If desired, a fibrous strand (not shown) may be arranged in the central hole 16 to assist in the drawing up of fuel 6. Such a strand may e.g. be made from ceramic fibres to retain the advantageous properties of a wick according to the present invention compared to wicks which decompose and produce soot.

Another embodiment of a wick 4 according to the invention is shown schematically in figures 8 and 9, the difference being the length of the wick 4. In the embodiment shown in figure 9, the suction end 5 of the wick 4 does not necessarily extend to the fuel reservoir 2, and the fuel 6 may be drawn from the reservoir 2 and to the suction end 5 of the wick 4 by fibrous material 20 extending to beyond the suction end 5 and into the fuel reservoir 2. The wick 4 comprises a cylindrical circumferential wall 17 and an upper lid 18 which form an enclosure 19 as shown in figure 10. The enclosure 19 contains a fibrous material 20 which is adapted to draw fuel 6 from the fuel reservoir 2 to the flame location end 7 of the wick 1 by capillary forces. The fibrous material 20 is not shown in figure 10 for clarity reasons. The fibrous material 20 may be made from ceramic fibres, but it may also be a material, such as cotton, which could burn. The fibrous material is protected from burning or decomposing by the lid 18 which is typically made from the same material as the circumferential wall 17, e.g. a ceramic material.

The wall 17 and the lid 18 may be manufactured as one piece, or the lid 18 may be a separate piece as shown in figure 10. Such a separate lid 18 may be fastened to the wall 17, e.g. by an adhesive, or it may rest loosely on top of the wall 17, e.g. in a recess in the upper edge of the wall 17. The lid 18 comprises a number of holes 21 through which the fuel 6 is drawn to the outer surface for burning. The size of the holes 21 is chosen to ensure that the fibrous material 20 is prevented from burning and such that only an appropriate amount of fuel is drawn to the flame. Figure 11 shows schematically a top view of a possible design of a lid 18 of the wick 4 shown in figures 8 and 9. However, the lid 18 may also be made with a number of e.g. circular holes through which the fuel 6 is drawn. Such holes may be arranged as shown for the channels 8 in figures 2 and 3, or they may be arranged in a more evenly dispersed pattern across the surface.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. E.g. the wicks are all shown as having a substantially circular cross section. However, any cross sectional shape is considered to be covered by the present invention as long as at least one of the objects is met.

A fuel burner 1 according to the present invention may comprise more than one wick 4.

The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

Claims

1. A wick for a fuel burner, said wick being adapted to draw up fuel by utilizing capillarity from a reservoir to a flame location end at which the drawn-up fuel is intended for being burnt, said wick comprising one or more inner channels extending from a suction end of the wick for suction of the fuel from the reservoir, to the flame location end of the wick for producing a flame of the drawn-up fuel, said one or more inner channels each having a substantially tubular-shaped inner surface.

2. A wick according to claim 1, wherein each of the one or more channels is a slit.

3. A wick according to claim 2, wherein each slit extends from a longitudinal axis of the wick and in a direction perpendicular to the longitudinal axis in any cross section of the wick.

4. A wick according to claim 3, wherein the wick is assembled from at least two wick parts so that slits are established between facing surfaces of the wick parts.

5. A wick according to any of claims 2 to 4, wherein the thickness of the one or more slits is between 0.05 and 2 mm, such as between 0.05 and 0.5 mm, between 0.5 and 1 mm or between 1 and 2 mm.

6. A wick according to any of claims 2 to 5, further comprising an elongated cavity along the longitudinal axis of the wick.

7. A wick according to claim 1, wherein at least some of the channels have a circular or oval cross section.

8. A wick according to claim 1, wherein at least some of the channels have a polygonal cross section, such as a quadratic cross section.

9. A wick according to claim 1, wherein at least some of the channels have an annular cross section, preferably a circular or oval cross section.

10. A wick according to any of the preceding claims, wherein all of the channels have substantially the same cross sectional shape and size.

11. A wick according to any of claims 1-9, wherein the channels constitute at least 5 two sets of channels, and the channels in each set of channels have substantially the same shape and size, which differs from either/both the shape and/or size of channels in the other one or more sets of channels.

12. A wick according to any of claims 7 to 11, wherein the channels are arranged 10 equidistant from an axis of symmetry of the wick and with a regular angular distance between adjacent channels.

13. A wick according to claim 11 when dependent on any of claims 7 to 9, wherein the channels in each set of channels are arranged equidistant from an axis of

15 symmetry of the wick and with a regular angular distance between adjacent channels.

14. A wick according to any of claims 7 to 13, said wick being made from at least one tubular-shaped rod and one or more massive or hollow other rods, wherein at

20 least one tubular-shaped rod encircles the one or more other rods, and wherein at least one channel is formed between the rods.

15. A wick according to any of the preceding claims, said wick comprising at least 10 inner channels, such as 10-20 inner channels, or 20-30 inner channels, or 30-

25 40 inner channels.

16. A wick according to claim 1, comprising a circumferential wall and a lid together at least partly forming an enclosure encapsulating a fibrous material adapted to draw up the fuel, wherein the lid comprises at least one through-going

30 hole through which fuel can be drawn from the fibrous material to the flame locating end.

17. A wick according to claim 16, wherein the size of the at least one hole and the thickness of the lid are so that the fibrous material is protected from burning or

35 decomposing when the wick is in use.

18. A wick according to claim 17, wherein the fibrous material is selected from : glass, ceramic, cotton, and carbon.

19. A wick according to any of claims 16 to 18, wherein the lid comprises at least 5 10 holes, such 10 to 100 holes.

20. A wick according to any of the preceding claims, said wick being made from a ceramic material.

10 21. A wick according to claim 20, said wick being made from aluminium oxide or titanium oxide.

22. A wick according to any of the preceding claims, said wick being produced by rod extrusion.

15

23. A fuel burner comprising a fuel reservoir and a wick according to any of claims 1-22, the wick being arranged to draw up fuel from the fuel reservoir.

24. A fuel burner according to claim 23, further comprising a support member at 20 least partly surrounding at least a part of the length of the wick and having an inner surface corresponding to an outer surface of the wick.

25. A fuel burner according to claim 23 or 24, wherein the flame location end of the wick extends beyond the support member.

25

26. A fuel burner according to any of claims 23 to 25, wherein the fuel burner is an oil lamp for indoor and/or for outdoor use.