Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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WOOD F'ED BARBECUE APPARATUS
FIELD OF THE INVENTION
The present invention re.Iates generally to the field of cooking devices. More
y 5 particularly, it concerns 'a portable wood fed barbecue apparatus
comprising a
combustion system using wood as the main source of fuel:
a BACKGROUND OF THE INVENTION
Vllith the ever increasing cost of oil products and the threat of supply
shortages,
interest in alternate forms of heating has increased in recent years. Wood
being a
14 renewable resource is a popular alternative and as a result a preponderance
of wood
burning stoves has emerged.
Barbecue apparatuses comprising a burner using wood as the main source of fuel
.. - , are already known in the prior art. Such barbecue apparatuses typically
comprise a
15 casing having an open top for supporting a cooking grill and a bumet
located in the
' casin under the cookie
9 g grill. The burner, which is tubular, comprises a combustion
chamber located over an air chamber, and a diffuser plate provided with air
openings
separating the combustion chamber from the air chamber. The air chamber has a
forced-air intake operatively connected tv a ventilation system that provides
forced-
air to the air chamber. In operation, pieces of wood are placed in the
combustion
.: chamber vn the diffuser ptafie and light. The fan is then turned on to
maintain the
.;
combustion of the wood. Examples of such prior art wood fed barbecue cooking
devices are found in fhe Applicant's prior patent applications VId09908048 and
v W09907~67 arid in US patents Nos 4,94,847 and 4,747,781.
25 .
WO 99/07287 discloses a grill assembly (12) comprising a housing (30)
including a
cooking surface (32}, sidewalls (34) skirting the cooking surface (32) and a
bottom
' wall (3t?) including an inlet (38} adapted to be sealingly connected to a
source of heat
.
to prevent heat loss and to promote collection of the heat in the housing
(30). This
30 documentfurther discloses a.bumer (14) mounted an a dome-shaped member (79}
A ,
.set on the bottom wall (17) of the container (16). The dome-shaped member
(79)
with the bottom wall ('!7) of tha container (16) arc def;n;ng an air-receiving
chamber
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(70) devised to provide air in the combustion chamber (60) of the burner for
the
combustion of a fuel therain.
The grill assembly (12) of WO 99/07267 also comprises sidewalls (18) of the
casing
which are slanted at not mere than 100° with.respec~to the base wall pf
the casing.
Consequently, the radiation emitted from the burner can hardly be reflected
upwards
towards the grill.
Also known in the art are US patents no. US 4,924,84 and US 4,747,7$1 which
14 describe a wood stove and.a cooking unit in which virtually complete
combustion is
~ achieved by feeding combustion air under pressure through openings in a
difFuser
plate with the diameter of the openings having a calculated size and spacing
therebetween. Although the problem of complete and clean combustion has been
a
solved by such wood fed barbecue cooking devices, several drawbacks remain
associated with their use.
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CA 02491092 2004-12-29
WO 2004/004527 PCT/CA2003/001004
2
One of these drawbacks is due to the loss of radiant energy/heat generated by
the
burner of these prior art cooking devices. These devices generate a
significant
amount of radiant energy/heat which is emitted from the sides of the burner.
This
energy loss is considerable and consequently entails the use of a greater
amount of
combustible material or wood in order to fuel the fire inside of the burner.
The radiant
energy/heat so generated also contributes to compounding the problems and
safety
hazards associated with the extreme temperatures that the external shields of
these
cooking devices typically reach, often over 600°F.
Another drawback associated with the prior art barbecue cooking devices is
inherent
to the barbecue cooking surface itself. The temperature of the cooking surface
is
typically very uneven. Indeed, the heat and temperature of that parfi of the
cooking
surface and/or grill located directly above the fire and/or flames are
generally much
more intense than those found at the corners or outward edges of the cooking
surface which are not situated directly above the fire and/or flames. This
entails that
barbecued foods are often unintentionally charred, burned, overcooked or
undercooked. Therefore, the uneven heat and temperature of the cooking
surfaces
of such prior art barbecue devices constitutes an additional and major
inconvenience
that makes barbecuing foods such as meats to the desired doneness a guessing
game for even the most experienced cook.
There is therefore a need for an improved wood fed cooking device. More
specifically, there is a need for a cooking device that would provide for less
radiant
energy/heat loss, for an evenly heated cooking surface and for lower
temperatures
reached by the external shields of the device.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a barbecue cooking device
that
satisfies at least one of the above mentioned needs.
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Accordingly, that object is achieved with a barbecue cooking device (1 )
comprising. . - .
-an inverted frustum casing (10) of a given height (11), having a base wall
(~0), an open top (3D) and a slanted side wall (40) section extending from the
' ~ base wall (2D) to the top (30) and having an inner surface (5D) made of a
material
capable of reflecting radiant energy;
-a grill (6D) mountable on the open top (30);
-a cup-shaped burner (7D) with a bottom wall (72) and a side wall section
(74),
' the burner (7D) comprising:
20 -a combustion chamber (76) in an upper portion thereof for burning a
I
. combustible material, thereby emitting thermal energy;
-an air chamber (78),located beneath the combustion chamber (7fi),
the air chamber (7S) having an air intake (82) for receiving air; and
-a diffuser plate (t'9) separating the combustion chamber (78) and the
2 5 air chamber (78); and
.; - a blower {90) operatively connected to the air intake (~2) of the air
chamber (~8) to provide forced-air tv the air chamber (7S);
' . the barbecue cooking device (1) being characterized in that:
-the side wall section (4!a) of the casing (1fl) extends at an angle
2 o ranging from about 135 degrees tv about 11 D degrees with respect to the
.;
base wall .(2D) of the casing (10);
' -the burner (TD) is located inside the casing (10) with said side wall
section (74) of the burner (70) spanning the height (11) of the casing (10)
.. ,
such that most of the thermal energy emitted by the combustion chamber (7fi)
25 radiate radially towards the slanted side,wall section (40) of the casing
(10)
where it is reflected towards the grill (60) mounted on the top of the casing
(1 t~); and
v ~-the blower (90) is part of a ventilation system (91) that further
comprises:
.' 30 -a pressurized air chamber (95) located downstream of the
blower (90), said pressurized air chamber (95) having an outlet end
'i {93) distal from the blower (9D); and
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-an air intake tube (98) having an open top end (99) secured to
v ~ the air intake ($2) of the air chamber (78); and an open b~ottvm end
(92) adapted to,be connected to the outlet end (93) of the pressurized
air chamber (95).
.i 5
Thanks to the configuration of the cooking device with the 6umer being located
.entirely within the casing with its side wall section spanning the height of
the casing,
the use of radiant energy radiating from the burner is optimized.
1o The inverted frustum casing may have the shape of an inverted cone or
pyramid,
However in accordance with a preferred embodiment it has the shape of an
inverted
pyramid. More preferably, the burner is generally tubular and has a round
bottom
wall. However, the burner may also have a generally rectangular shape with a
rectangular bottom wall.
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4
Also preferably, the bottom wall of the burner covers more than 50% of the
surface
area of the casing's bottom wall. Even more preferably, it covers more than
75%.
In accordance with a preferred aspect, the barbecue cooking device comprises a
heat deflecting shield mountable beneath the grill on top of the burner for
deflecting
flames emitted from the burner.
Still preferably, the deflecting shield is sized to cover substantially all of
the surface
area of the grill. In that case the deflecting shield is also used for
diffusing the
thermal energy reflected towards the grill, thus providing. an evenly heated
cooking
surface.
More preferably, the deflecting shield has a central portion free of slits,
and a
peripheral portion having a series of longitudinal slits. In use, when the
shield is
mounted beneath the grill, the central portion is located on top of the
burner. Even
more preferably, the longitudinal slits of the shield are in a staggered
arrangement
with respect to the longitudinal slots of the grill.
According to another aspect of the present invention, the slanted side wall
section
of the casing extends at an. angle ranging from about 135 degrees to about 110
degrees with respect to the base wall of the casing. More preferably, that
angle is
120 degrees.
According to yet another preferred aspect of the present invention, the
barbecue
cooking device comprises means for cooling the slanted wall section.
Preferably, the
cooling means comprises an air inlet located in a lower portion of the slanted
wall
section for allowing air to enter into the casing and an air outlet located in
an upper
portion of the slanted wall section for allowing air to exit the casing,
thereby allowing
a flow of air that cools the slanted wall section. More preferably, the air
inlet and the
air outlet consist of a plurality of openings provided in the slanted side
wall.
As can be appreciated, a cooking device according to the invention provides
for less
radiant energy/heat loss. Furthermore, some preferred embodiments of the
invention
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WO 2004/004527 PCT/CA2003/001004
provide for an evenly heated cooking surface and for lower temperatures
reached
by the external shields of the device.
BRIEF DESCRIPTION OF THE DRAWINGS
5 These and other objects and advantages of the invention will become apparent
upon
reading the detailed description and upon referring to the drawings in which
Figures 1 A and B are perspective views of the barbecue device according to a
first
preferred embodiment of the invention showing the grill handle in an assembled
(B)
and a disassembled position (A).
Figure 2 is an exploded perspective view of the barbecue cooking device shown
in
figure 1.
Figure 3 is a cross sectional side view of the barbecue cooking device shown
in
figures 1 and 2.
Figure 4 is an exploded perspective view of the grill and casing of a barbecue
cooking device according to a second preferred embodiment of the present
invention.
2o
Figure 5 is a top view of a grill according to a further preferred embodiment
of the
barbecue cooking device of the present invention.
Figure 6 is a top view of a deflecting shield to be used with the grill shown
in figure
2 5 5 according to a further preferred embodiment of the barbecue cooking
device of the
present invention.
Figure 7 is a top view of the grill of figure 5 with the defecting shield of
figure 6 shown
in dotted lines.
Figure 8 is a side view of the grill and deflecting shield shown in figure 7.
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6
Figure 9 is a perspective view of a burner according to a further preferred
embodiment.
While the invention will be described in conjunction with example embodiments,
it will
be understood that it is not intended to limit the scope of the invention to
such
embodiments. On the contrary, it is intended to cover all alternatives,
modifications
and equivalents as may be included as defined by the appended claims.
DESCRIPTION OF PREFERRED EMBODIMENTS
In the following description, similar features in the drawings have been given
similar
reference numerals and in order to lighten the figures, some elements are not
referred to in some figures if they were already identified in a preceding
figure.
Referring to any one of figures 1 to 9, a barbecue cooking device (1)
according to
the invention comprises an inverted frustum casing (10) of a given height (11
) having
a base wall (20), an open top (30) and a slanted side wall section (40)
extending
from the base wall (20) to the top (30). The embodiment illustrated preferably
has an
inverted pyramidal shape and thus comprises four of said side walls (40). The
inner
surface (50) of these side walls (40) are made of a material capable of
reflecting
radiant energy, as for example steel, aluminum, copper. The casing (10) is
preferably
2o mounted on a base support (12).
The barbecue (1) further comprises a grill (60) mountable on the open top (30)
and
a cup-shaped burner (70) located inside the casing (10). The burner (70) has a
bottom wall (72) and a side wall section (74) delimiting a combustion chamber
(76)
located in an upper portion of the burner and an air chamber (78) located
beneath
the combustion chamber (76). A diffuser plate (79) is separating the
combustion
chamber (76) and the air chamber (78). The air chamber (78) has an air intake
(82)
operatively connected to a blower (90) to provide forced-air to the air
chamber (78).
The combustion chamber (76) is used to receive and burn a combustible material
such as wood whereas the air chamber (78) provides the air necessary to burn
the
combustible material. The blower (90) is part of a ventilation system (91)
that
comprises the blower (90) driven by an electric motor (94), and a power supply
(96)
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WO 2004/004527 PCT/CA2003/001004
7
that provides power to the electric motor (94). The power supply (96) is
preferably
DC cells or batteries. Although not clearly illustrated, the ventilation
system (91)
comprises an opening for receiving air from outside. The ventilation system
(92) also
comprises an air intake tube (98) having an open top end (99) adapted to fit
in the
air intake (82) of the air chamber (78) and an open bottom end (92) adapted to
be
connected to an outlet end (93) of a .pressurized air chamber (95) located
downstream from the blower (90).
In use, pieces of wood (not illustrated) are placed on the diffuser plate (80)
in the
combustion chamber (78) and lighted. Then, the blower (90) is turned on, to
draw the
1 o air from outside into the ventilation system (91 ). The blower (90) forces
the air into
the air intake tube (98) and then into the air chamber (78) of the burner (70)
where
air under pressure is forced through the perforated diffuser plate (79) to
promote
combustion of the wood.
As can be appreciated, the burner (70) is located inside the casing (10) with
its side
wall section (74) spanning the height of the casing (10) such that most, and
preferably all of the thermal energy emitted by the combustion chamber (76)
radiates
radially towards the slanted side wall section (40) of the casing (10) where
it is
reflected towards the grill (60) mounted on top of the casing (10).
~0
Thanks to the specific configuration of the barbecue cooking device (1) of the
invention, the use of thermal energy radiating from the burner (70) is
optimized.
Indeed, a majority of the radiant thermal energy emitted radially from the
side wall
section (74) of the burner (70) is able to effectively reach the inner surFace
(50) of the
slanted walls (40) of the casing (10). This thermal energy is thus
recuperated, and
reflected upwardly to the cooking surface or grill (60) as will be discussed
further
herein below. Therefore a certain proportionality and proximity are required
between
the side wall section (74) of the burner (70) and the inner surface (50) of
the slanted
side wall section (40) of the casing (10) as discussed herein and shown in
figures 1
to 3. This is understandable for the proper operation of the barbecue cooking
device
(1) of the present invention.
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8
It is worth mentioning that although the casing (10) of the embodiment
illustrated has
an inverted pyramidal shape, it may also have an inverted conical shape or any
other
shape that allows and provides for a slanted side wall section (40) as well as
for the
convenient insertion of a centrally located burner (70), and that without
departing
from the scope of the present invention.
Most preferably the burner (70) has a generally tubular or cylindrical shape
and a
round bottom wall (72) as shown in figure 9. However, as shown in figures 1 to
3, the
burner (70) may also have a rectangular shape with a rectangular bottom wall
(72).
More preferably, in order to obtain the desired proximity between the side
wall
section (74) of the burner (70) and the inner surface (50) of the slanted side
wall
section (40) , the surface area of the bottom wall (72) of the burner (70)
covers more
than 50% of the surface area of the base wall (20) of the casing (10). More
preferably still, the surface area of the bottom wall (72) of the burner (70)
covers
more than 75% of the surface area of the base wall (20) of the casing (10).
Such
relative surface area proportions between the side wall section (74) of the
burner (70)
and the slanted side wall (40) section of the casing (10) allow for most of
the radiant
thermal energy that is radially emitted from the side wall section (74) of the
burner
(70) to effectively reach the inner surface (50) of the slanted side wall
section (40)
2 0 of the casing (10). Thanks to the material of the inner surface (50) of
the slanted side
wall section (40), the radiant thermal energy that reaches the slanted side
wall
section (40) of the casing (10) is reflected upwardly toward the entire
cooking
surface or grill (60). The radiant thermal energy which would otherwise be
lost is
therefore conveniently and advantageously recuperated and used for cooking
purposes. The effective area of the cooking surface or grill (60) is also
therefore
conveniently widened instead of being limited to a central portion of the
grill (60)
situated directly over and above the fire.and burner (70). This feature of the
invention
provides a further advantage over the prior art barbecue devices.
3 o The slanted side wall section (40) of the casing (10) is preferably at an
angle ranging
from about 135 degrees to about 110 degrees with respect to the base wall (20)
of
the casing (10). More preferably, the angle is 120 degrees. As discussed, such
a
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9
slant in the side wall section (40) combined with an inner surface (50) made
of a
material capable of reflecting radiant thermal energy allows for efficient
upward
reflexion of the radiant thermal energy emitted from the side wall section
(74) of the
centrally located burner (70). Persons skilled in the art will readily
recognize suitable
materials for reflecting radiant thermal energy toward the cooking surface and
the
grill (60). Radiant thermal energy is therefore conveniently recuperated
instead of
lost as in the prior art devices.
According to a still preferred aspect of the invention, the inverted frustum
casing (10)
1o is made of several sheets of a suitable material. These sheets may be
partially
folded over each other at the edges and welded together as shown in figure 4.
However, the casing (10) may also be made of a single piece of suitable metal
or
material, as mentioned above, according to methods of manufacture also well
known
to persons skilled in the art.
Many grills and cooking surfaces are known and may be used with the barbecue
apparatus of the present invention. In fact, any grill or equivalent cooking
surface
suitable for barbecuing foods may be used with the apparatus of the present
invention. It is therefore understood herein and throughout the application,
that the
expression "grill" encompasses any and all grills as well as any and every
other
equivalent cooking surface suitable for use with barbecue.
Referring to figures 1 to 3, according to a further preferred aspect of the
present
invention, the barbecue cooking device (10) comprises a heat deflecting shield
(100)
that is mountable beneath the grill (60) on top of the burner (70) for
deflecting flames
emitted from the burner (70). This shield prevents foods from being rapidly
charred
or burned by the flames of the burner while being consistently undercooked in
the
peripheral area of the grill. More preferably, the deflecting shield (100) is
provided
with slits (102) as shown in figures 1, 2, 6, 7 and 8. These slits
advantageously
3 o deflect and direct flames emitted from the burner to a location in between
the heat
deflecting shield (100) and the cooking surface or grill (60). Therefore heat
of the
flames is more evenly distributed throughout the cooking surface area situated
above
CA 02491092 2004-12-29
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the heat deflecting shield (100). More preferably still, the deflecting shield
(100) is
sized to cover substantially all of the surface area of the grill (60), for
diffusing the
thermal energy reflected toward the grill (60). The inventors have found that
the heat
deflecting shield (100) captures the reflected thermal energy, evenly and
uniformly
5 diffuses and distributes it throughout the entire surface of the shield
(100) and
upwardly emits radiant thermal energy toward the cooking surface or grill
(60). The
purpose of the heat deflecting shield (100) of the present invention is
therefore three-
fold. It acts simultaneously as a heat captor, diffuser/distributor, as well
as a heat
radiator. This feature provides an other convenient advantage over.the prior
art
10 barbecue devices which typically present important temperature variability
across the
cooking surface, especially between the central portion, situated directly
above the
burner, and the peripheral portion and corners. The present inventors have
found
that the present invention provides for a uniformly and evenly heated cooking
surface, with as little as +/- 50°F temperature variation between the
corners and the
central portion of the cooking surface. This is a considerable improvement
over the
prior art devices.
Turning now to figures 5, 6, 7 and 8, and in accordance with another preferred
embodiment of the invention the heat deflecting shield (100) has a central
portion
(104) free of slits, and a peripheral portion (106) having a series of
longitudinal slits
(102) which are in a staggered arrangement with respect to longitudinal slots
(108)
of the grill (60), the central portion (102) being located on top of the
burner (70) when
the deflecting shield (100) is mounted beneath the grill (60). This
arrangement
contributes to shield the cooking surface from the open flame.
According to yet another preferred aspect of the present invention, the
barbecue
cooking device (1) comprises means for cooling the slanted side wall section
(40).
A non limiting example of such means is given herein but any other equivalent
means may be used. Referring to figure 4, the cooling means comprises an air
inlet
(110) located in a lower portion of the slanted wall section (40) of the
casing (10) for
allowing air to enter into the casing (10) and an air outlet (120) located in
an upper
portion of the slanted wall section (40) for allowing air to exit the casing
(10), thereby
CA 02491092 2004-12-29
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11
allowing a flow of air that cools the slanted wall section (40). More
preferably, the air
inlet (110) and air outlet (120) consist of a plurality of openings provided
in the
slanted wall section (40) of the casing (10). Such openings (110, 120) serve
the
purpose of creating a chimney effect whereby cool air enters into the casing
(10)
through the bottom openings (110), travels upwardly along the inner side (50)
of the
slanted wall section (40) and exits through the upper openings (120). The
chimney
effect so-created thereby reduces even more the temperature reached by the
exterior of the casing (10).
1o The present inventors have found that the exterior of the casing (10) of
the present
invention reaches temperatures of about 300°C with such openings and
slanted
reflective inner surface whereas the prior art barbecue device casings
typically reach
over 600°C. Therefore, the combination of the slanted wall section
(40), inner surface
(50) made of a material capable of reflecting radiant energy and openings
(110, 120)
provide distinct advantages over the prior art devices.
Referring to figures 1 A and B, the device also preferably comprises a handle
(130)
for removing the grill (60).The handle (130) is preferably removably
connectable to
the grill (60), as best shown for example in referring to figure 1 B. More
specifically,
the handle (130) comprises a fork-shaped portion (132) with a grasping means
for
grasping the grill (60) as shown in figures 1 A and B.
As shown in figures 1 to 4, when the grill (60) has to be removed from the
casing
(10), for example when the burner (70) have to be cleaned, the handle (130) is
~5 connected to the grill (60) which then can be removed.
The burner (70) is such as described in US 4,924,847. However, any other
equivalent burner which may be suitably and conveniently inserted into the
barbecue
cooking device may be used. The burner of US 4,924,847 operates on the
principle
3o that air is delivered to the combustion zone in a specific and controlled
manner so
as to optimize combustion. The air is injected to form a thin combustion zone
through
a series of jets or openings in a plate where the jets have a specific size
and are
CA 02491092 2004-12-29
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12
arranged in a specific configuration in order to produce interaction between
air flows:
efficient combustion results. In practice the system includes a closed
diffuser which
has an upper plate having the aforementioned jets and a lower plate separated
from
the upper plate and attached thereto by side members so as to form a type of
manifold. A conduit feeds into an opening in the lower plate and is connected
to
means for providing air under pressure to the diffuser. The solid fuel, such
as wood,
rests on the upper surface of the diffuser, and after ignition, burns in a
controlled
manner, by regulating fihe flow rate of the air to the combustion zone. The
air under
pressure may be supplied by an air pump in which case the flow of air is
dictated by
1o the size of the orifices or jets while the output of the pump controls the
velocity at
which that flow of air is injected into the combustion zone. The upper surface
of the
diffuser plate is provided with raised portions which hold the solid fuel off
the jets in
the plate as otherwise the air flow of some of the openings would be blocked.
The
raised portions are located between each opening in the plate, and the
openings are
arranged in a regular pattern as also described in US4,924,847.
Although preferred embodiments of the present invention have been described in
detail herein and illustrated in the accompanying drawings, it is to be
understood that
the invention is not limited to these precise embodiments and that various
changes
2 o and modifications may be effected therein without departing from the scope
or spirit
of the present invention.
