Burner for liquid fuel cell

A die-cut wick for use in the burner of a disposable fuel cell formed from a single sheet of wicking material so that the wick has two symmetrical half-sections situated on either side of a vertical center line and which are folded along the center line into a face-to-face alignment. Each half-section further includes an elongated lower body segment containing a horizontally-disposed upper edge, a narrow neck segment centered on the upper edge of the body segment and a tab vertically extending therefrom to a given height. The neck is slidably received within a burner of a fuel cell so that it can be raised or lowered between limits to control the flame height and the amount of heat produced by the burner. The tabs are foldable toward and away from each other to further control the flame geometry and distribution of the heat.

BACKGROUND OF THE INVENTION 
This invention relates to a liquid fuel cell and, in particular, to a 
die-cut wick for use in a liquid fuel cell. 
A die-cut wick for use in a liquid fuel cell is described in U.S. Pat. No. 
4,611,986. The wick includes two symmetrical half-sections that can be 
folded in face-to-face alignment along a vertical center line. Each 
half-section further includes a lower body segment that has a horizontal 
top edge and a narrower upper tab segment centered upon the top edge of 
the body segment. 
In assembly, the tabs are folded together and passed upwardly through the 
stem of a burner situated in the lid of a liquid fuel cell. The tabs are 
extended until the top edges of the body segments are arrested by the 
inside surface of the lid. The body segments are fanned out and glued to 
the inside of the lid to fix the tabs at a desired height above the lid. 
The body segments pass downwardly into the cell card carry fuel stored 
therein to the tabs by capillary action. In operation, the tabs are 
lighted and the amount of heat produced by the burner is controlled by 
adjusting the relative positions of the two tabs by folding them toward or 
away from each other. 
The folded wick arrangement has worked well in practice and has shown 
itself to be a simple approach to controlling the flame, thus the heat 
output of a liquid fuel cell. The amount of control afforded by the fixed 
height tab, however, is limited. Gluing the body of the wick to the 
underside of the lid is not totally satisfactory in that the bond can be 
broken enabling the wick to be repositioned in the cell. The tabs of the 
wick will, under certain conditions, become over-saturated with fuel 
causing the lid of the cell to be wetted with fuel. The problem of 
over-saturation of a wick-equipped, disposable liquid fuel cell is 
addressed in U.S. Pat. No. 4,526,530. As disclosed in this patent, the 
stem of the burner is surrounded by a circular trough in which excess fuel 
is collected The trough has one or more ports that open into the fuel cell 
container to permit the excess fuel collected in the trough to drain back 
into the cell. The burner utilized in this fuel cell is rather complex and 
relatively expensive to manufacture thus raising the cost of the 
disposable cell. 
SUMMARY OF THE INVENTION 
It is a primary object of this invention to improve liquid fuel cells. 
Another object of the present invention is to provide greater control over 
the flame height and amount of heat produced by a liquid fuel cell. 
Still another object of the present invention is to provide an improved, 
foldable die-cut wick that is suitable for use in a liquid fuel cell. 
A further object of the present invention is to provide a foldable die-cut 
wick for use in a liquid fuel cell that affords the user control over the 
flame height, the amount of heat produced by the cell, the flame geometry 
and the distribution of heat. 
A still further object of the present invention is to prevent wetting of 
the lid of a liquid fuel cell which is equipped with a foldable wick. 
Yet a further object of the present invention is to provide a relatively 
inexpensive burner for use in a disposable fuel cell which provides a wide 
range of control over the flame and heat produced by the cell. 
These and other objects of the present invention are attained by means of a 
liquid fuel cell equipped with a wick that is die-cut from a sheet of 
wicking material so that the wick has two symmetrical half-sections 
situated on either side of a vertical center line. Each half-section 
further contains a lower body segment and an upper tab segment that are 
connected by a narrower neck segment having a pre-determined length. In 
assembly, the wick is folded along the center line and the neck of the 
wick is slidably contained within a vertically-disposed stud that forms 
part of the cell's burner. The length of the neck is greater than the 
height of the stud thus allowing the wick to be raised and lowered within 
the burner to control the flame height and the amount of heat that is 
produced by the cell. In addition, the tab segments of the wick can be 
folded or unfolded to provide further control over the flame geometry and 
distribution of heat. A trough surrounds the burner stud and collects 
excess fuel that might leak from the wick in the event it becomes 
over-saturated. The collected fuel is returned to the cell by means of 
drain holes.

DESCRIPTION OF THE INVENTION 
Liquid fuel cells are generally used for warming foods and to provide 
intimate table lighting. Oftentimes, the user will attempt to either 
extend the wick to produce a higher or hotter flame or to push the wick 
down into the burner to reduce the flame or conserve fuel. Many of these 
fuel cells are disposable and are equipped with relatively inexpensive 
burners in which a wick is held in place at a given height a tight fit of 
the wick within the wick stand. Any attempt to adjust the wick usually has 
a deleterious effect on the wick and the operation of the burner and gives 
results that are quite unpredictable. Relatively small changes in wick 
exposure can cause great changes in flame height and the resulting 
illumination or heat. Also, overextending the wick can result in a flame 
that consumes more fuel than the wick can deliver, causing fuel starvation 
and ultimate burning of the wick. As will be explained below, the present 
invention involves a very low cost burner for use in a liquid fuel cell 
which contains a die-cut wick for providing the user with a predetermined 
and assured range of control over flame height and the amount and 
distribution of the heat. 
Referring now to the drawings, a liquid fuel cell, generally referenced 10, 
is illustrated in FIG. 1. The fuel cell includes a container 11 having a 
cylindrical side wall 12 and a bottom wall 13. The container is adapted to 
store a quantity of liquid fuel. The top of the container is closed and 
sealed by means of a lid 14. A burner 15 is centrally mounted in the lid 
and a wick 16 slidably contained within the burner. Although not shown, a 
plastic cap is usually provided with the fuel cell to enclose the top of 
the wick. The cap is press-fitted onto the burner and thus shields and 
protects the wick when the fuel cell is not being used or is packaged for 
shipment or storage. 
As illustrated in FIG. 2, the burner 15 is formed from a single sheet of 
material, preferably metal, and is mounted within an opening 20 formed in 
the lid 14. A vertically-disposed, cylindrical stud 22 is situated in the 
center of the burner and is surrounded by an annular trough 25. A series 
of drain holes 32--32 are formed in the bottom wall 33 of the trough. The 
outer wall 26 of the trough in raised to an elevation that is slightly 
higher than that of the stud. The burner further includes a top wall 28 
and an outside side wall 29 which is in parallel alignment with the outer 
wall 26 of the trough. The lower edge of side wall 29 is equipped with a 
flange 30 which is situated over the opening 20 formed in the lid. The 
bottom edge 31 of wall 29, which protrudes from the opening, is 
mechanically crimped tightly in metal to metal contact against the bottom 
surface of the lid to establish a leak-tight joint. Any other suitable 
means, such as soldering or the like, may be employed to join the burner 
to the lid. 
Turning now to FIG. 3, there is shown in greater detail the construction of 
the wick 16 that is used in the burner 15. The wick is die-cut from a 
single sheet of wicking material and includes two symmetrical 
half-sections 31--35 that are foldable about a vertical center line 37. A 
vertical slit 38 is cut in the wicking material along the center line to 
facilitate folding the half-sections into face-to-face alignment when the 
wick is mounted in the burner. 
Each half-section includes a lower body segment 40 and an upper tab segment 
41 that are joined by a narrow neck 42 which is centered upon both the 
body segments and tab segments. Each tab is a triangular-shaped member 
having the base of the triangle lying upon the edge 46. The three corners 
of the triangle are truncated as shown in FIG. 3. The top edge 45 of the 
body segment and the bottom edge 46 of the tab segment extend laterally 
beyond the side edges of the neck to provide relatively wide upper and 
lower shoulders for the neck. The vertical length of the neck is greater 
than the vertical height of the burner above the lid and the distance 
across the shoulders is greater than the outside diameter of the 
vertically-disposed stud 22. 
In assembly, the wick is folded along the center line 37 to place the 
half-sections in face-to-face alignment. The tabs are then passed upwardly 
through the stud until the lower edge 46 clears the top of the stud. The 
width across each neck segment is about equal to the inside diameter of 
the stud so that the neck segments substantially fill the area within the 
stud. As noted above, the length of each neck segment is greater than the 
vertical height of the stud thereby permitting the wick to be slidably 
repositioned within the burner. The extent of vertical travel afforded the 
wick is controlled by the upper and lower shoulders which are arranged to 
contact the top of the burner and the bottom of the wall 33 of the trough, 
respectively. Adjusting the height of the tabs allows for control over the 
flame height and thus the amount of heat produced by the burner. In 
addition to being able to adjust the height of the wick tabs, the tabs can 
be folded away from or toward each other to further control the flame 
geometry and the distribution of heat. 
As best seen in FIG. 1, the lower body segments of the wick extend 
downwardly into the container and are allowed to fan out. The length of 
each segment is greater than the depth of the container so that the bottom 
of the wick rests upon the bottom of the container. The fanned segments 
absorb liquid fuel stored in the container and move it upwardly to the 
tabs via capillary action. As previously noted, the top section of the 
wick that is situated above the stud can become over-saturated with fuel 
under certain conditions. Due to the construction of the present burner, 
any overage of fuel is collected within the trough and then returned to 
the container via the drain holes 32--32. The inner wall of the trough 
formed by the stud 22 is lower in elevation than the outer wall 26. This 
insures that any overabundance of fuel will spill over the stud back into 
the container rather than over the outer wall of the burner thus 
preventing fuel from wetting the lid. 
While this invention has been described in the specification and 
illustrated in the drawings with reference to the preferred embodiments, 
it is not confined to the details set forth and this application is 
intended to cover any modifications and changes that may come within the 
scope of the following claims.