Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1'~77879
1 BAR~ECUE GRILL
2 ~ackground of the Invention
3 This invention relates to gas barbecue grills
4 for outdoor use. More particularly, this invention
relates to gas barbecue grills in which liquified
6 petroleum gas is supplied under pressure to a duct in
7 which gas and air are intermixed, the mixture then
8 flowing lnto a plenum chamber in which the gas and air
9 are more thoroughly mixed, the mixture then flowing
upward through a multiplicity of holes in a burner
11 plate to burn at the surface of that plate, oreating
12 heat and infrared radiation for cooking food placed on
13 a grid located above the burner plate.
14 Convéntional gas barbecue grills typically
comprise a box-like shell having a bottom, four sides,
16 and an open top, to which is attached a cover. Across
17 the open top is a grid for supporting food to be
18 cooked. Below the grid is a grate on which refractory
19 briquettes are placed. Below the briquettes are one
or more metal gas burners, having a plurality of small
21 holes, to which gas and air are fed through a
22 venturi. The gas is typically supplied to the venturi
23 at a pressure of between about 4 inches and about 11
24 inches of water. Also typically, the gas is supplied
from a high pressure cylinder of liquid petroleum gas,
26 through a pressure regulator which reduces the gas
27 pressure to that desired. The burning gas-air mixture
28 heats the briquettes, and combustion products pass
29 upward through the grid supporting the food. The
purposes of the briquettes are to distribute the heat
31 evenly across the underside of the grid, to insulate
32 the gas flames from interference by wind, and to
33 provide a surface on which liquids from cooking foods
34 can be vaporized to enhance the flavor of the foods.
~. ~
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1'~77879
1 Another type of conventional gas barbecue
2 grill incorporates perforated refractory burner
3 elements. Pressurized gas is supplied through
4 venturis to plenum chambers together with air to form
a combustible mixture which passes through holes in
6 the refractory and is ignited and burns on the outer
7 surface of the burner elements. The elements are
8 heated sufficiently to emit convective and infrared
9 radiation.
One problem with both types of conventional
11 barbecues is their susceptibility to w~nd currents.
12 Drafts tend to extinguish the flames, and consequently
13 cumbersome baffling and other means are required to
14 protect the burners. Another problem, particularly
prevelant in barbecues using perforated refractories,
16 is heat distribution. Heat is not distributed
17 uniformly over the food cooking surface. A third
18 problem, also particularly prevalent in barbecues
19 using perforated refractories, is flashback -
combusion below the burner surface. A fourth problem
21 in conventional barbecue grills is the difficulty in
22 cleaning them. Food and liquids drip into the grill
23 container and accumulate in the bottom. No convenient
24 means is provided to remove the parts of the barbecue
grill or to access the inside bottom of the container.
26 Summary of the Invention
27 The barbecue grill of this invention solves
28 each of the above problems. The barbecue grill of
29 this invention comprises, in one embodiment, a
contalner having upstanding sidewalls forming a cavity
31 having an upper opening. A cover is attached to the
32 container, movable to a closed position over the
33 opening, and to an open position in which the opening
34 is exposed. A substantially horizontal food-holding
grid is suspended from the sidewalls proximate the
36 upper opening. Between two opposed sidewalls are
37 supported two support rods in a generally horizontal
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1 position. Suspended from and between the two rods are
2 two heat generating systems. Each system comprises a
3 plenum chamber open at the top and having a gas inlet
4 port. Each plenum chamber carries a burner plate over
substantially all of the top opening. The burner
6 plate comprises at least two ceramic tiles separated
7 ~y an imperforate metal plate. The ceramic tiles have
8 a plurality of holes therethrough to allow the passage
9 of gas out from the plenum chambers. A metal tube
carried by the metal plate facilitates the propagation
11 of gas from one tile to another over each plenum
12 chamber. I
13 In one embodiment, the barbecue grill of this
14 invention comprises a cast aluminum container about 11
inches high, about 17 inches deep, and about 26 inches
16 wide, open at the top, with a cast aluminum cover
17 hinged at the back of the container. Liquid petroleum
18 gas is supplied from a pressurized system, such as a
19 conventional propane cylinder. The gas passes through
a pressure regulator, which reduces the gas pressure
21 to about 40 inches of water. The gas is then injected
22 through a gas inlet orifice of about 0.03 inches in-
23 diameter, into two cylindrical ducts, each of which24 communicates with a plenum chamber. The duct walls
have air inlet opening~ downstream of the gas inlet
26 orifice. It is important to note that the duct
27 differs from a conventional venturi in that it has a
28 generally uniform cross-sectional area, and that no
29 baffle or other means of adjusting the size of the air
openings is provided. In the typical low pressure gas
31 burner, gas enters through a venturi which also draws
32 in air for combustion. The air vent in such an
33 arrangement incorporates a baffle so that the amount
34 of air entering the system can be regulated. In
conventional low pre~sure systems, a baffle is
36 desirable because the ~ize of the air vent is critical
37 to control the degree of combustion. The margin of
38 error in sizing the air vent is quite small. Small
39 differences in gas pressure require changes in the
1 sizing of the air vent to provide the proper
2 gas-to-air ratio. It has been found that in the high
3 pressure system of this invention, no means for
4 modulating air flow is required. Satisfactory
combustion occurs with fixed air inlets even with
6 typical fluctuations in gas pressure experienced when
7 using bottled gas.
8 The gas-air mixture passes from each duct into
9 one of the plenum chambers in which the gas and air
are intimately mixed. The plenum chambers comprise
11 sheet metal boxes having generally trapezoidal ends
12 connected by generally planar sides of generally equal
13 size and a generally planar horizontal base. In one
14 end of the plenum is the gas inlet port, through which
the plenum communicates with the duct. The plenum is
16 open at the top.
17 Proximate the upper edges of each of the
18 plenum ends is a bracket adapted to engage a metal
19 rod, from which the plenum chamber is removably
suspended. A front rod and a rear rod, generally
21 parallel to one another, extend between opposite sides
22 of the container. The rods are removably supported by
23 the container sides by brackets carried by the
24 container sides. The plenum chambers are suspended
between the rods in side-by-side relationship.
26 The top edges of the ends and sides of the
27 plenum form a generally rectangular upper wall in a
28 generally horizontal plane, forming the top opening
29 about 9 inches by about 9 inches. The plenum carries
a burner plate which substantially covers the top
31 opening. The burner plate comprises two generally
32 rectangular ceramic tiles of about 9 inches by about 3
33 1/2 inches, separated by a metal plate of about 9
34 inches by about 2 inches. The ceramic tiles are about
1/2 inch thick, and are perforated by about 200 holes
36 per square inch of tile, the holes being of about 0.05
37 inch in diameter. The metal plate is imperforate.
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1 The surfaces of the ceramic tiles are generally fl~t.
2 The upper surfaces can be slightly scalloped to
3 increase the effective surface area for infrared
4 radiation and to help shield the flame from wind. The
gas-air mixture from the plenum passes up through the
6 holes in the ceramic tiles, and is burned proximate
7 the upper surface of the tiles. The metal plate
8 carries a gas transfer tube, which serves to propagate
9 gas across the metal plate from one tile to another
during initial ignition of the gas.
11 Above the burner plates are reverberation
12 screens to intensify the infrared radiation and to
13 help shield the flames from wind currents. The
14 reverberation screens comprise wire mesh screens
suspended about 1/2 inch above the burner plates.
16 Above the reverberation screens are conventional food
17 support grids, on which food is placed for cooking.
18 In the preferred embodiment, a rotisserie
19 burner extends generally horizontally along the inside
of the back wall of the container. The burner
21 comprises a generally cylindrical metal tube having a
22 series of gas discharge orifices arranged horizontally
23 and slightly above the level of the upper surface of
24 the reverberation screens. In one end of the burner
is a gas inlet, comprising a venturi and air inlet
26 holes. The other end of the burner is closed and
27 terminates within the container. The rotisserie
28 burner facilitates ignition of the gas-air mixture
29 discharged from the burner plates, a~ is more fully
described below.
31 The sides of the container form a generally
32 rectangular lower opening of about 16 inches by about
33 10 inches. The sides carry brackets proximate the
34 opening, from which is slidably suspended a drawer
which is adapted to cover the opening in a closed
36 position, and to be removable from the container.
1~77879
1 The use of a high pressure gas feed, a
2 uniquely configured gas duct and plenum chamber,
3 burner surface spacers of high heat conductivity, and
4 an enclosure open at the bottom with a removable
drawer, together with other aspects of the barbecue
6 grill of this invention explained in more detail
7 below, result in a novel barbecue grill without the
8 limitations of conventional barbecue grills.
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1 ~r ~lle~r~ tion of ~he Drawings
2 Fig. 1 is a front perspective view, in partial
3 cutaway, of one embodiment of the barbecue grill of
4 this invention.
Fig. 2 is a top plan view of the container
6 portion of the barbecue grill shown in Fig. 1, with
7 the cover removed, with the reverberation screen shown
8 in partial cutaway, with a horizontal section through
9 the righthand transfer tube, and with the third burner
bracket removed to show the third burner with a
11 portion of the discharge holes.
12 Fig. 3 is a cross sectional view taken on
13 lines 3-3 of Fig. 2, with the third burner bracket in
14 place.
r
Fig. 4 is a cross sectional view taken on
16 lines 4-4 of Fig. 3.
17 Fig. 5 is an enlarged fragmentary cross
18 sectional view of the view shown in Fig. 4 with the
19 reverberation screen removed.
Fig. 6 is a cross sectional view taken on
21 lines 6-6 of Fig. 5.
22 Fig. 7 is a fragmentary top plan view of a
23 tile.
24 Fig. 8 is an fragmentary cross sectional view
taken on lines 8-8 of Fig. 7.
26 Fig. 9 is a schematic diagram of the barbecue
27 grill of this invention.
28 Fig. 10 is a fragmentary top plan view of one
29 plenum chamber, with the reverberation screen removed,
and the screen support and tile partially shown.
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1 Fig. 11 is a top plan view of the drawer.
2 Fig. 12 is a partial cross sectional view
3 kaken on lines 12-12 of Fig. 5.
4 Fig. 13 is a partial sectional view taken on
lines 13-13 of Fig. 5.
6 Fig. 14 is a front view of the ~et, taken on
7 line 13-13 of Fig. 13 with the duct and frame not
8 shown.
9 Fig. 15 is a partial side view of the
container, showing the drawer clo~ed, and open in
11 dotted lines.
1~77~'7~:3
1 p~s~r~iQ~ Qf th~_Pre~erred ~mbQd~en~
2 The following is a description of the
3 preferred embodiments of this invention. It is to be
4 understood that the dimensions recited herein describe
the preferred of many embodiments, and that the
6 dimensions can be proportionately increased or
7 decreased to provide a novel and effective barbecue
8 grill within the scope of this invention.
9 Referring to Figs. 1-4, the preferred barbecue
grill of this invention comprises a cast aluminum
11 container 1 with a cast aluminum cover 2. The
12 container comprises upstanding sidewalls 3 including a
13 front wall 4, rear wall 5, and opposite side walls 6,7
14 forming a cavity 8 about 11 inches deep and about 12
inches by about 20 inches at the bottom of sidewalls
16 6,7. The sidewalls 3 extend upwardly and outwardly,
17 terminating in an upper edge 9 which defines a
18 generally rectangular opening about 17 inches by about
19 26 inches. Formed in sidewalls 3 is a front ledge 10
and a rear ledge 11, adapted to support cooking grid
21 12, which is about 16 inches by about 25 inches, in a
22 generally horizontal position. Food is placed on
23 cooking grid 12 to be cooked. Cover 2 is hinged to
24 rear wall 5. Cover 2 comprises a generally box-like
structure having outwardly pro~ecting handles 13 by
26 which cover 2 may be raised and lowered. In its
27 lowered position, walls 14 of cover 2 engage sidewalls
28 3 to substantially cover the upper opening in
29 container 1 formed by edge 9. Vent 15 in cover 2
allows combustion products to leave the grill when
31 container 1 is closed by cover 2.
32 Front wall 4 also defines a pair of openings
33 16, each of which receives a gas inlet duct 17. Gas
34 inlet ducts 17 comprise metal pipes of generally
symmetrical cross-section, having linear axes
36 generally parallel to the side walls 6,7 of container
37 1. It is preferred that duct~ 17 comprise aluminized
1'~77~79
1 20 gauge cy~indrical tubes about 4 inches long and
2 about 1 inch O.D. In one end of each of ducts 17 is a
3 gas jet 20. As can best be seen in Figs. 13 and 14,
4 gas jet 20 comprises a plug 21 having a gas discharge
orifice 22 therethrough. Extending radially from the
6 central portion of plug 21 are vanes 23, which serve
7 to locate jet 20 in duct 17 such that orifice 22 is
8 located on the axis of duct 17. Jet 20 is sized to
9 fit snugly in duct 17, with outer surfaces 24 of vanes
23 tightly engaging inner surface 2~ of duct 17.
11 Shoulders 27 on vanes 23 engage end surface 28 of duct
12 17, to locate jet 20 longitudinally in duct 17. When
13 jet 20 is received by duct 17, vanes 23 and inner
14 surface 25 define secondary air inlet orifices 30,
through which air is drawn to be mixed with gas
16 entering duct 17 through orifice 22.
17 Jet 20 also bears female threaded portion 31,
18 into which a male threaded fitting 32 is fit to
19 connect duct 17 through gas supply line 33 and
associated gas valve 19 to a pressure regulator which
21 is connected to a source of compressed gas. Jet 20 is
22 secured to container 1 by nut 34. Nut 34 is threaded
23 onto fitting 32 and bears on frame 35 affixed to front
24 wall 4. Frame 35 comprises a generally planar front
wall 38 having a pair of holes 28 therein aligned with
26 ducts 17. Wall 38 is spaced from front wall 4 and is
27 generally perpendicular to the longitudinal axis of
28 duct 17. Frame 35 is affixed to container 1 by any
29 convenient meanq, as by welds or bolts. Fitting 32
passes through hole 28 in frame 35 and is threaded
31 into jet 20. Rear face 29 of ~et 20 bears on the side
32 of frame 35 opposite nut 34, to secure ~et 20 in
33 place. Because duct 17 is rigidly affixed to
34 components within container 1, as is described below,
it is preferred that hole 28 be sized to allow for
36 minor variations in position of duct 17 to facilitate
37 assembly of the barbecue grill.
l~77a~7s
1 It is preferred that ends 36 of vanes 23 be
2 about 0.125 inches wide and that surface 37 of ~et 20
3 define a radius of about 0.5 inches, to define the
4 appropriate size of air inlet orifices 30 for a gas
pressure of 40 inches of water. It is to be
6 understood that for a particular heat and radiation
7 output, the diameter of orifice 22 is a function of
8 the pressure of the gas supplied to jet 20. The
9 preferred pressure range is from about 20 inches of
water to about 60 inches of water. As the pressure of
11 gas supplied to jet 20 is increased, the s~ze of
12 orifice 22 should decrease to maintain the desired
13 mass flow rate of gas through duct 17. With the
14 preferred gas, propane, at the preferred gas pressure
of 40 inches of water, the preferred orifice 22 size
16 is 0.031 inches in diameter to generate a maximum of
17 about 15,000 BTU/hour. At those specifications, the
18 mass flow rate is 5.88 cubic feet per hour of propane
19 gas. The appropriate sizing of orifice 22 at other
gas inlet pressures is a matter of routine trial and
21 error.
22 Duct 17 is provided with a pair of primary air
23 inlet vents 40, downstream of the outlet of orifice
24 22. Vents 40 are generally rectangular in
configuration, and located on opposite sides of duct
26 17. Vents 40 are sized to allow sufficient air to
27 enter duct 17 for substantially complete combustion.
28 In the preferred embodiment, with gas pressure at 40
29 inches of water and with an orifice 22 size of 0.031
inches, vents 40 are approximately 1.125 inches by 0.7
31 inches.
32 It is desired that carbon monoxide production
33 be minimized. At present, the Canadian Gas
34 Association standard is 80 ppm carbon monoxide in the
burner effluent gases. The dimensions noted above for
36 orifice~ 30 and vents 40 yield an effluent carbon
37 monoxide content of about 30 ppm at a gas inlet
38 pressure of about 40 inches of water. A "Drager
11
1~77879
1 meter was used to ~easure carbon monoxide content in
2 an air-free sample of combustion products. The
3 air-to-fuel ratio is about 2.5. For gas pressures
4 different from 40 inches of water, the sizes of
orifices 30 and vents 40 must be increased or
6 decreased proportionately.
7 Duct 17 communicates with plenum chamber 45,
8 so that the gas-air mixture exiting duct 17 enters
9 plenum chamber 45 and is intimately mixed. Duct 17 is
fixed at one end by jet 20 affixed to frame 35 as
11 noted above. Duct 17 passes through an opening 16 in
12 front wall 4 and through gas inlet port 48 in front
13 wall 49 of plenum chamber 45. In the preferred
14 embodiment, duct 17 is affixed to plenum chamber 45 by
bracket 53, the top portion 51 of which is welded to
16 duct 17 and the bottom portion 52 of which is welded
17 to floor 55 of plenum chamber 45. Duct 17 fits snugly
18 through inlet port 48, to minimize the passage of gas
19 or air through the interface of wall 49 and duct 17.
It is preferred that front wall 49 form a generally
21 cylindrical flange 54 about 1/4 inch high about the
22 circumference of port 48, which fits over duct 17. It
23 is also preferred that duct 17 project about one inch
24 into plenum 45, and that the longitudinal axis of duct
17 be generally perpendicular to wall 49. Primary air
26 inlet vents 40 are located between plenum 45 and front
27 wall 4.
28 As discussed above, ~et 20 comprises plug 21
29 having a gas discharge orifice 22, and radial vanes
23. The location of the gas discharge outlet of
31 orifice 22 with respect to inner surface 25 of duct 17
32 and with respect to a~r inlet orifices 40 is
33 important. The gas discharge outlet of orifice 22
34 should be generally centrally located in duct 17 and
aligned such that the gas is discharged as a jet
36 stream in a line generally parallel to the axis of
37 duct 17. As noted above, it is preferred that duct 17
38 comprise a generally cylindrical tube having a linear
12
1'~778'~9
1 axis. It is preferred that orifice 22 comprise a
2 generally cylindrlcal passage through plug 21 having
3 an axis generally parallel to the axis of duct 17,
4 exiting at front face 26 of plug 21. It is alqo
preferred that front face 26 be generally
6 perpendicular to the axis of duct 17. Vents 40 should
7 comprise rectangular cut-outs in duct 17, of
8 substantially the same dimensions, aligned with one
9 another on opposite sides of duct 17. For a gas inlet
pressure of about 40 inches of water, the following
11 dimensions are preferred: duct 17 has an inside
12 diameter of about 1 inch; orifice 22 has a diameter of
13 about 0.031 inches; vents 40 have a total area of
14 about 1.6 inches; air inlet orifices 30 should be
sized as noted above; and the distance from face 26 to
16 vents 40 should be about 1 1/16 inches.
17 As noted above, since the dimensions of the
18 system are a function of the gas pressure adopted, the
19 dimensions reoited above are specific to a gas
pressure of 40 inches of water. In general terms, the
21 following dimensions are preferred: the distance
22 between face 26 and vent 40 should be between about
23 0.8 to about 1.2 the inside diameter of duct 17; the
24 diameter of duct 17 should be between about 20 to 50
times the diameter of orifice 22; the ratio of gas
26 pressure, in inches of water, to vent 40 total area,
27 in ~quare inches, should be between about 20 and 30;
28 and the distance duct 17 extends into plenum 45 should
29 be between about 5S to about 30S of the distance
between walls 49 and 50 of plenum 45.
31 Projecting about 1 3/4 inches from front wall
32 49 is shield 56, which is intended to prevent food and
33 liquid whic~ falls into container 1 from entering duct
34 17 through air vents 40. Shield 56 comprises inclined
roof portion 57 and vertical sides 58. Tabs 59
36 extending from sides 58 are tack welded to front wall
37 49, to secure shield 56 to plenum 45.
1'~778~9
1 A pair of plenum chamber3 45 are suspended in
2 container 1. In the preferred embodiment, plenum
3 chambers 45 are substantially identical. Each of
4 plenum chambers 45 preferably comprises a sheet metal
box-like structure having a floor 55, a front wall 49,
6 a rear wall 50, and inclined sides 60, of 20 gauge
7 aluminized steel. Port 48 is located in front wall
8 49, with its axis about 1 inch above floor 55 and
9 centrally located between sides 60. It is preferred
that plenums 45 comprise 20 gauge aluminized steel,
11 with generally trapezoidal front and rear walls 49,
12 50, generally rectangular sides 60, and a generally
13 rectangular floor 55. Plenum chambers 45 are
14 preferably about 3 1/2 inches deep and about 3 inches
wide at floor 55.
16 As can best be seen in Figs. 4, 5, and 10,
17 walls 49,50 and sides 60 bear shoulder 65 about 1/4
18 inch wide in a generally horizontal plane about the
19 perimeter of plenum 45. Located outwardly from
shoulder 65 are generally vertical walls 66 adjacent
21 to sides 60 and generally vertical walls 67 ad~acent
22 to front and rear walls 49 and 50. Walls 66 and 67
23 are about 3/4 inch high and end in top wall 68 about
24 1/2 inch wide in a generally horizontal plane. Walls
66 and 67 together form a generally rectangular upper
Z6 opening in plenum 45 about 9 inches on each side. A
27 single baffle 70 is located in plenum 45, comprising
28 an L-shaped member having a first leg tack welded to
29 rear wall 50 and a generally horizontal second leg 71,
pro~ecting generally perpendicularly to wall 50 about
31 1 3/4 inches, about 1 inch below shoulder 65.
32 Each plenum 45 carries a burner plate 72 which
33 substantially completely covers the upper opening of
34 each plenum 45, and which are supported by shoulder
65. Each burner plate 72 comprises at least two tiles
36 74 of low heat conductivity, each tile 74 having a
37 plurality of holes 75 through which the gas-air
38 mixture from plenum chamber 45 flows. Combustion of
14
1'~77~79
1 the gas occurs proximate the burner surface 76 of
2 tiles 74, and heats the bùrner surface sufficiently
3 that infrared radiation is emitted. It is preferred
4 that tiles 74 comprise equal sized generally flat,
rectangular ceramic blocks about 1/2 inch thick, about
6 8 3~4 inches long by 3 1/2 inches wide, having
7 cylindrical holes 75 about 0.05 inches in diameter
8 perpendicular to burner surface 76 and generally
9 uniformly distributed thereover. It is preferred that
each of the tiles 74 comprise a single, integral
11 ceramic tile of the dimensions stated. However, each
12 of tiles 74 can comprise two or more ceramic blocks
13 placed adjacent to one another to form a tile 74 of
14 the desired dimensions. It is especially preferred
that the tiles have about 200 holes per square inch of
16 surface area, by perimeter measurement, and that the
17 holes be about 0.0515 inches in diameter. It is also
18 especially preferred that the tiles have a thermal
19 conductivity of between about 0.002 and about 0.003
cal.~sec./cm2/cm C, measured at between 20C
21 and 100C. It is necessary that tiles 74 be able to
22 withstand the operational temperatures of the barbecue
23 grill of this invention, ie., a temperature at burner
24 surface 76 of between about 1600 degrees F. and about
1800 degrees F. Such a tile is available from
26 Hamilton Porcelains Limited, Brantford, Ontario.
27 In general, it is desirable that a barbecue
28 grill produce a generally uniform distribution of heat
29 over the cooking grid surface. The barbecue grill of
this invention employs four devices to uniformly
31 distribute heat and radiation over grid 12: 1) plenum
32 chambers 45 are located in spaced relationship from
33 sidewalls 6,7, front wall 4, and rear wall 5 within
34 cavity 8; 2) tiles 74 are separated by spacers to
strategically locate tiles 74 within cavity 8; 3)
36 tiles 74 are slightly angled away from one another,
37 and; 4) heat and radiation are produced uniformly over
38 tiles 74 as a result of the shape and size of plenum
1'~77~7't
1 chamber 45 and the location of baffle 70. Each of
2 these devices is explained in more detail below.
3 In the preferred embodiment, each plenum 45
4 carries a pair of tiles 74 separated by a spacer 79.
5 Spacer 79 comprises an imperforate metal sheet,
6 preferably stainless steel, the same length as the
7 tiles (8 3/4 inches), carried by plenum 45 between
8 each pair of tiles 74. It is preferred that spacer 79
9 comprise a sheet of 20 gauge 430 stainless steel. As
can best be seen in Figs. 4, 6 and 10, spacer 79
11 comprises a generally planar portion 80, generally
12 flush with burner surface 76, generally parallel
13 downwardly depending walls 81 generally perpendicular
14 to portion 80, outwardly projecting legs 82 generally
15 perpendicular to walls 81, and end caps 83 which
16 enclose the ends of the channel created by portion 80
17 and walls 81. It is preferred that portion 80 be
18 about 2 inches wide, thus creating a separation
19 between pair of tiles 74 of about 2 inches. Walls 81
20 are adjacent to inside edges 85 of tiles 74, and legs
21 82 underlie tiles 74. It is preferred that walls 81
22 be about 5/8 inches high, and that legs 82 be about
23 1/4 inch wide.
24 As can best be seen in Figs. 5 and 10, outside
25 edges 86 of tiles 74 rest ad~acent to shoulder 65 and
26 wall 67. Ends 88 of tiles 74 and end caps 83 are
27 adjacent to wall 66. It is preferred that a gasket 90
28 reside about the perimeter of tiles 74, to prevent the
29 escape of gas about the interface of tiles 74 and
plenum 45 and spacer 79 and to minimize thermal
31 conduction between tiles 74 and plenum chamber 45. It
32 is also preferred that a gasket reside between end
33 caps 83 and wall 66, to minimize thermal conduction
34 between spacer 79 and plenum 45 and to prevent the
flow of gas-air mixture around tiles 74 rather than
36 through holes 75. If tiles 74 comprise multiple
37 pieces of ceramic, a gasket should be interposed
38 between the pieces to prevent gas leakage. A suitable
16
1'~7'7879
1 gasket is "Fibrefraxn, a silicon oxide-alumina
2 material, about 1~8 inch thick.
3 It is preferred that burner plate 72 be fitted
4 onto plenum 45 such that spacer portion 80 is
generally horizontal and tiles 74 face away from one
6 another slightly. Referring to Fig. 4, it is
7 preferred that burner surfaces 76 slope away from
8 portion 80 at an angle of from about 1 degree to about
; 9 5 degrees. The appropriate slope can be conveniently
accomplished by sizing tiles 74, spacer 79, and gasket
11 90 such that their total width is slightly greater
12 than the distance between walls 67. In that manner,
13 inside edges of tiles 74 and legs 82 of spacer 79 are
14 raised slightly above shoulder 65. During heating and
cooling spacer 79 and tiles 74 expand and contract, at
16 different rates. Gasket 90 acts as an expansion
17 joint. During extended use gasket 90 may lessen in
18 thickness Shoulder 65, which is continuous about the
19 perimeter of plenum 45, prevents burner plates 72 from
collapsing into plenum 45.
21 In operation, the gas-air mixture flowing
22 through tiles 74 is ignited to produce a low,
23 generally continuous flame proximate burner surface
24 76. The gas may be ignited by any of various means,
such as with a match, a torch, or with an electronicly
26 produced spark. To facilitate the ignition of gas
27 flowing through both tiles 74 of each plenum 45, gas
28 transfer tubes 92 are provided. It is preferred that
29 tubes 92 comprise U-shaped members about 1/2 inch
high, 1/2 inch wide, and 2 inches long having lateral
31 wings 93 which are tack welded to spacers 79 to form
32 passages through which gas can flow from one tile 74
33 across spacer 7g to adjacent tile 74. It is preferred
34 that tube 92 extend completely across spacer 79 such
that ends 94 are ad~acent tiles 74.
36 In a less preferred embodiment, a series of
37 perforations is provided in spacer 79 in lieu of tube
1'~77879
1 92. Gas flows through the perforations, allowing the
2 flame front to pass from one tile 74 to the adjacent
3 tile 74.
4 As can best be seen in Figs. 2 and 4, front
wall 49 and rear wall 50 of plenum chambers 45 each
6 carry a wall 95 which depends downwardly from top wall
7 68, which, with wall 66, creates inverted U-shaped
8 suspension brackets 98 about 1/2 inch wide along the
9 top of front wall 49 and rear wall 50. It is
preferred that brackets 98 be formed as an integral
11 part of plenum chamber 45, as by stamping. Each of
12 brackets 98 is adapted to receive rod 100, and to
13 support plenum chambers 45 therefrom. Rods 100
14 comprise generally straight steel rods about 23 inches
long and about 5~16 inches in diameter. Each of side
16 walls 6, 7 carries a front support bracket 102 and a
17 rear support bracket 103, all four of which lie
18 generally in a horizontal plane. Preferably support
19 brackets 102 and 103 comprise U-shaped members
integrally cast or welded to sidewalls 3. Front
21 support brackets 102 and rear support brackets 103 are
22 each adapted to support one rod 100 therebetween, in
23 generally parallel relationship. Plenum chambers 45
24 are suspended by suspension brackets 98 between rods
100 in side-by-side relationship.
26 In an alternative, less preferred, embodiment,
27 plenum chambers 45 can be provided with brackets 98 on
28 sides 60. Two pairs of rods 100 extend between front
29 wall 4 and rear wall 5, a plenum chamber 45 being
suspended between each pair. By this means, plenum
31 chambers 45 can be located at different heights within
32 cavity 8. ~owever, it is understood that in the
33 preferred embodiment, plenum chambers 45 can be
34 located at different heights within cavity 8 by use of
non-linear rods having a high portion to accomodate
36 one plenum chamber 45 and a low portion to accomodate
37 the other plenum chamber 45, and by locating the pair
38 of support brackets 102,103 supporting the low portion
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1 on side wall 6 at a lower height than corre~ponding
2 support brackets 102,103 on the opposite side wall 7.
3 By suspending plenum chambers 45 from rods
4 100, and suspending rod~ 100 from sidewalls 3, the
barbecue grill of this invention can be very easily
6 assembled and disassembled. By loosening rut 34 and
7 removing fitting 32 from plug 21, plenum chamber 45,
8 duct 17, and plug 21 can be lifted as a single
9 assembly from support rods 100 and removed from
container 1. Support rods 100 can then be removed
11 from container 1. Of course, pler,um chambers and rods
12 100 can be so located that plenum chambers 45 can be
13 lifted from rods 100 and removed from container 1
14 without the necessity of loosening any other parts of
the grill. In that case, plenum chambers 45 would be
16 located on rods 100 such that plenum chambers 45 could
17 be moved away from front wall 4 sufficiently to
18 release duct 17 from plug 21 without having to release
19 plug 21 from frame 35.
It is notable that no drain or opening is
~1 required in floor 55 of plenum chambers 45, to remove
22 liquids and particles which might accumulate in
23 chambers 45. Although burner plates 72 are located
24 below grid 12, separated only by reverberation screens
115, no substantial accumulation of liquids or food
26 particles occurs in chamber 45. During operation of
27 the grill of the invention, tiles 74 reach sufficient
28 temperature to vaporize substantially all food and
29 liquids which drop onto their surfaces. As noted
above, reverberation screen 115 prevents larger food
31 particles from reaching burner surface 72. Even when
32 the grill is not in use accumulation in chambers 45 is
33 unlikely. It has been found that rain water does not
34 accumulate readily in chambers 45. Reverberation
screens 115 tend to shield tiles 74 by scattering rain
36 drops so that they hit tiles 74 at an angle, lessening
37 the likelihood of water entry through holes 75. In
38 addition, the surface tension of water tends to create
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1 water droplets of a size greater than holes 75.
2 Angling tiles 74 away from one another also tends to
3 reduce accumulation of materials within chambers 45.
4 In any event, the novel construction of the barbecue
grill of this invention facilitates removal of
6 material which may accumulate in chambers 45. Plenum
7 chambers 45 can be easily lifted from support rods 100
8 and inclined so that any accumulated material falls
9 from chambers 45 through ducts 17.
As noted above, it is desirable to distribute
11 the heat and infrared radiation uriformly over the
12 surface of cooking grid 12. As can be seen in Fig. 2,
13 tiles 74 together form a generally rectangular
14 horizontal pattern generally centrally located in
cavity 8. Each of the four tiles 74 is located in a
16 corner of that pattern, spaced ~rom one another and
17 from sidewalls 3. The pattern formed by tiles 74 is
18 generally dimensionally proportional to the exterior
19 dimensions of grid 12. Edges 86 of tiles 74 are
generally equally spaced from front wall 4 and rear
21 wall 5, and ends 88 of tiles 74 are generally equally
22 spaced from sidewalls 6,7 and from one another on
23 adjacent plenum chambers 45. Spacers 79 separate
24 tiles 74 on each plenum chamber 45. Tiles 74 are
angled slightly away from one another on each plenum
26 45.
27 The location of plenums 45 away from sidewalls
28 6,7 and front and rear walls 4,5, serves a function in
29 addition to uniform distribution of heat and
radiation. By suspending plenums 45 in cavity 8,
31 plenums 45 are surrounded by air passages which
32 provide air to burner ~urfaces 76 and which also cool-
33 plenums 45, thereby reducing the risk of flashback or
34 spontaneous ignition withi~ plenums 45. More
importantly, thermal contact between burner surfaces
36 76 and container 1 is minimized, providing a barbecue
37 grill whi~h is much cooler at the exterior surfaces of
38 container 1 than would otherwise be the case.
~0
1'~7'787'3
1 Also important is the surface area of tiles 74
2 relative to the cooking grid 12 area. It is preferred
3 that the total tile 74 surface area be from a~out 25%
4 to about 50% of the cooking grid 12 area, both areas
calculated by perimeter measurement. It is most
6 preferred that the ratio of tile 74 area to grid 12
7 area be about 0.3. Similarly, the ratio of tile 74
8 surface area to burner plate 72 surface area is
9 important. It is preferred that the tiles 74 comprise
from about 50S to about 90S of the burner plate 72
11 area. It is most preferred that the tiles 74 ~urface
12 area comprise about 75S of the burner plate 72 surface
13 area, both surface areas calculated on the basis of
14 perimeter measurements.
The even distribution of heat and radiation
16 over the area of grid 12 is also a function of the
17 heat and radiation production pattern over the surface
18 of tiles 74. It is preferred that heat and radiation
19 production be distributed uniformly over the area of
tiles 74. To this end, the size and shape of plenum
21 chamber 45, and the location of baffle 70, is
22 important. Plenum chambers 45 must be large enough in
23 volume to properly mix the gas and air which enter
24 through duct 17. In addition, the gas-air mixture
must flow through tiles 74 at a generally unform rate
26 over the area of tiles 74. A higher flow rate in one
27 location, or an excessively rich gas-air mixture, will
28 create a hot spot in tile 74. Finally, plenum chamber
29 45 must be dimensioned such that flashback does not
occur.
31 Flash back - or ignition of the gas-air
32 mixture within plenum 45 - occurs if the flow rate of
33 the gas-air mixture through tiles 74 is less than the
34 flame propagation rate, or if spontaneous ignition
occurs within plenum 45 because of excessive
36 temperatures within plenum 45. The gas flow rate
37 through tiles 74 is a function of the total
1'~77879
1 cross-sectional area of the holes therethrough. At
2 the particular gas flow rate necessarly to produce
3 sufficient radiation and heat for cooking (in this
4 case, about 15,000 BTU's per hour maximum per plenum
45), the temperature within plenum 45 is a function of
6 the volume of plenum 45, and the heat transfer between
7 burner surface 72 and plenum 45. The use of
8 insulation, as noted above, reduces heat transfer from
9 burner surface 72 to plenum 45. It has been found
that the configuration of plenum 45 intimately mixes
11 the gas and air entering through duct 17 to produce a
12 particularly uniform heat and radiation distribution
13 pattern over tiles 74, while minimizing flashback.
14 An appropriate plenum chamber 45 can be
15 generally described as follows: it has a generally
16 rectangular upper opening with a length (between walls
17 67) to width (between walls 66) ratio of from about
18 0.8 to about 1.2; a depth (from shoulder 65 to floor
19 55) to width (between walls 66) ratio of about 0.3 to
20 0.5; inclined sides 60 of generally equal size;
21 generally parallel trapezoidal front and rear walls 49
22 anp 50, respectively; a floor 55 geDerally parallel to
23 burner plate 72 of a width of from about 0.25 to about
24 0.4 times the width of the upper opening; a gas inlet
25 opening having a diameter from about 0.25 to about 0.4
26 the depth of the plenum, with its axis generally
27 equldistant from sides 60 a~d located a distance from
28 floor 55 from about 0.25 to about 0.4 the depth of
29 plenum 45; a gas-air inlet projecting into plenum 45
from about 0.1 to about 0.3 the distance between walls
31 49 and 50; a generally horizontal baffle extending
32 generally between sides 60, located a distance from
33 floor 55 about 0.5 to about 0.75 the depth of plenum
34 45, and projecting into plenum 45 from about 0.15 to
35 about 0.3 of the distance between front and rear walls
36 49,50.
37 Surprisingly, it has been found that spacers
38 79 do not increase the tendency of spontaneous
1'~7~78'79
1 ignition within plenum chambers 45. It had been
2 thought that placement of a relatively thin, high
3 thermal conductivity metal surface over plenum 45, in
4 close proximity to a relatively thick, low thermal
conductivity ceramic surface such as tiles 74, would
6 tend to increase the ambient temperature in plenum 45
7 to a degree that spontaneous ignition would occur.
8 During operation spacers 79 get hot enough to vaporize
9 most food and liquids which drop onto them, yet do not
reach sufficient temperature to cause spontaneous
11 ignition within plenum 45. Metal spacers 79 are
12 superior to ceramic spacers, since only the former
13 reach a high enough temperature to be self-cleaning.
14 Ceramic spacers of a thickness necessary for
structural support of tiles 74 would not reach a
16 temperature sufficient to incinerate food and liquids
17 which dropped onto them, and would accumulate
18 residue. In addition, when cleaning is necessary,
19 metal spacers 79 have sufficient structural strength
to withstand abrasion without the risk of breakage
21 inherent in ceramic spacers.
22 As can best be seen in Figs. 1, 3, and 6, a
23 pair of tile clips 110 is affixed to each plenum 45
24 along the upper portions of sides 60. In the
preferred embodiment, each tile clip 110 comprises an
26 L-shaped aluminized steel member about 8 inches long,
27 having a flrst leg 111 about 1 inch wide tack welded
28 to top wall 68 of side 60. Leg 111 projects
29 horizontally inward from wall 68 and ends in an
upwardly extending second leg 112 about 0.25 inch
31 high. Tile clips 110 serve to hold burner plate 72 in
32 place on plenum 45, and to support reverberation
33 screen 115 above burner plate 72.
34 Reverberation screen 115 comprises a generally
rectangular woven wire screen, having a horizontal top
36 surface 116 of similar dimensions to burner plate 72.
37 Reverberation screen 115 sits on second legs 112 above
38 burner plate 72, with sides 117 depending downward
1'~77879
1 about 0.5 inches toward burner plate 72.
2 Reverberation screen 115 serves to shield burner
3 surface 76 from wind currents, and to increase the
4 infrared radiation emitted by burner plates 72. It is
estimated that burner surface 76 temperature is
6 elevated by about 100 degrees F. by the use of
7 reverberation screen 1t5. In addition, reverberation
8 screen 115 prevents food particles having a dimension
9 larger than about 1~4 inch from falling onto tiles
74. Such food particles are suspended by
11 reverberation screen 115 and are incinerated, thereby
12 lessening the likelihood of plugging holes 75.
13 As can best be seen by Figs. 3, 4, and 11,
14 tray 120 is suspended below container 1 to catch food
and liquid which drops through container 1. ~idewalls
16 3 of container 1 converge with bottom wall 122 which
17 defines a generally rectangular opening 123 in
18 container 1 of about 16 inches by about 8 inches.
19 Depending from bottom wall 122 proximate and on either
side of opening 123 are a pair of parallel tray
21 runners 124. Each tray runner 124 comprises a
22 generally horizontal member 125 which is affixed to
23 bottom wall 122 by bolts or other means, a downwardly
24 depending vertical section 127, and an inclined ledge
128. Ledges 128 are adapted to clidingly engage
26 shoulders 130 of tray 120, to allow tray 120 to be
27 moved to a position under opening 123, and to allow
28 tray 120 to be withdrawn from container 1 for
29 cleaning.
Tray 120 comprices a generally planar
31 imperforate central rectangular portion 132 slightly
32 smaller in dimension than opening 123, inclined sides
33 134, inclined back 135, and inclined front 136, all
34 inclined upwardly and outwardly from central portion
132 at approximately the same angle. Inclined sides
36 134 have raised portions 138 which define air vents
37 140. Inclined back 135 has a similar raised portion
38 142 which defines front air vent 143, and also a
: 24
1'~7787~
1 handle 145 by which tray 120 can be moved. Air vents
2 140 are approximately 8 inches wide and 1/4 inch
3 high. Air vent 143 is approximately 10 inches wide
4 and 1~4 inch high.
In a less preferred embodiment, bottom wall
6 122 supports tray 120 within container 1. Opening 123
7 comprises a generally rectangular opening somewhat
8 smaller than tray 120. The lower portion of rear wall
9 5 is cut out to form a generally rectangular opening
in rear wall 5 as a continuation Or opening 123. The
11 opening in rear wall 5 is sized tolaccomodate back 135
12 when tray 120 is in its closed position. Bottom wall
13 122 forms a ledge within container 1 which slidably
14 supports sides 134 or portion 132 of tray 120. A
channel is carried on the inside surface of each side
16 wall 6,7, spaced from bottom wall 122 a distance
17 slightly greater than the height of tray 120, adapted
18 to slidably engage sides 134 to facilitate the
19 movement of tray 120 on bottom wall 122 over opening
123.
21 As noted above, gas at burner surfaces 76 can
22 be ignited by various mechanisms. Because of the
23 relatively large burner surfaces 76, the gas flow rate
24 at any point is relatively low. Although it is
possible to ignite the gas flowing through tiles 74
26 using a spark igniter, a match, or other conventional
27 means, a larger more intense point of ignition is
28 desirable. In the preferred embodiment, a third
29 burner system 150 is provided which functions as a
rotisserie burner and also as an igniter of gas above
31 the burner plates 72. Burner system 150 comprises a
3~ gas inlet pipe 151 having air openings 152, venturi
33 153, a tube 154 having gas discharge ports 155 along
34 its length and closed at its end 156 opposite venturi
153, and a bracket 157 by which tube 154 is affixed to
36 container 1. Gas burning at discharge ports 155
37 provides the larger more intense point of ignition
38 desirable for burner plates 72. Igniter port 158 in
1~7'~79
1 tube 154, and piezoelectric spark generator 166,
2 provide means to ignite the gas-air mixture discharged
3 from ports 155.
4 Tube 154 is preferably generally cylindrical,
about 18 inches long and about one inch outside
6 diameter. Tube 154 is preferably supported by bracket
7 157 in a generally horizontal position about 1.25
8 inches from rear wall 5 and adjacent to burner plates
9 72, as by bolts through bolt holes 165 in bracket
157. It is preferred that there be about 65 discharge
11 ports 155 through tube 154, each about 0.07 inches in
12 diameter, arranged in single file, equally spaced on
13 about 0.25 inch centers, along about 16 inches of the
14 length of tube 154, such that the gas-air mixture from
tube 154 is discharged through ports 155 over burner
16 plates 72. It is preferred that discharge ports 155
17 be located circumferentially on tube 154 between about
10 15 degrees above a horizontal plane passing through
19 the axis of tube 154 to about 10 degrees below the
horizontal plane, such that the gas-air mixture from
21 tube 154 is discharged over burner surfaces 76. It is
22 especially preferred that discharge ports 155 be
23 located generally on a horizontal plane passing
24 through the longitudinal axis of tube 154.
It is preferred that venturi 153 comprise an
26 inlet portion 159 about 0.375 inches long and an
27 outlet portion 160 about 2.25 inches long, ~oined by a
28 neck portion 161 about 0.56 inches in inside
29 diameter. It is also preferred that inlet pipe 151 be
abo~t 1.2 inches long, and that air openings 152
31 comprise two oppo~ite openings about 0.75 inches high
32 by about 0.03 to about 0.09 inches long.
33 Bracket 157 preferably comprises an L-shaped
34 member having a first leg 162 affixed to tube 154 and
having a second leg 163 affixed to rear wall 5. It is
36 preferred that a ~lame director 164 project at about a
37 45 degree angle from first leg 162. Flame director
26
1;~778'7'~3
1 164 co~prises an extension of first leg 162, extending
2 the full length of leg 162, and about 0.25 wide,
3 spaced about 2.25 inches from rear wall 5.
4 Igniter port 158 preferably comprises a slot
5 in tube 154 proximate the mid-portion of one of plenum
6 chambers 45. It is preferred that the slot be between
7 about 0. 02 inches and about 0.1 inches wide, begin
8 about 0.125 inches to about 0.5 inches about the
9 circumference of tube 154 from ports 155, and extend
between about 20 degrees and about 150 degrees about
11 the circumference of tube 154. It is most preferred
12 that port 158 be about 0.03 inches wide, beBin about
13 0.25 inches from ports 155, and extend more than 90
14 degrees circumferentially to about 45 degrees below a
15 horizontal axis through the axis of tube 154. Less
16 preferably, igniter port 158 can comprise a series of
17 apertures in tube 154 of between about 0. 02 inches and
18 about 0.1 inches in diameter and extending about the
19 circumference of tube 154 as noted above. In either
20 configuration, the critical points are that igniter
21 port 158 be sufficiently close to spark generator 166
22 that a spark from spark generator 166 can ignite gas
23 flowing from port 158, and that port 158 be
24 sufficiently close to discharge ports 155 that the
25 flame created at port 158 can be propagated to the gas
26 discharged from ports 155.
27 Discharge ports 155 necessarily have a greater
28 cumulative area for gas flow than igniter port 158,
29 since the former are intended to provide sufficient
30 gas to produce a flame sufficient for cooking food
31 placed on grid 12 or suspended from a spit abcve grid
32 12. Igniter port 158 is intended to act as a pilot
33 flame for burner system 150, and consequently need
34 only be of ~ufficient size and location to allow the
35 ignition of gas escaping therefrom by generator 166
36 and to ignite gas escaping from ports 155.
27
1~77879
1 During start-up operation, a valve, operated
2 by a control at the front of container 1, is opened to
3 allow gas to flow into inlet pipe 151. The gas can be
4 supplied from the same source which supplies burner
5 plates 72. Air is drawn through openings 152, and the
6 gas-air mixture flows through venturi 153 and into
7 tube 154. The gas-air mixture exits tube 154 through
8 discharge ports 155 and ignition port 158.
9 Piezoelectric spark generator 166, carried by rear
wall 5 adjacent to port 158 and operated by a control
11 at the front of container 1, ignites the gas as it is
12 discharged from port 158. Alternatively, or in
13 addition, an opening can be provided in rear wall 5
14 adjacent to port 158 to enable a user to insert a
15 match through rear wall 5 to light gas exiting port
16 158. Also alternatively, a second port 158 can be
17 provided adjacent to an opening in rear wall 5 for
18 manually lighting burner system 150. In either case,
19 because of the proximity of port 158 to ports 155, the
flame established along port 158 ignites the gas
21 discharged from ports 155.
22 Once a flame has been established at ports
23 155, one or both valves 19 can be opened to allow gas
24 to enter plenums 45 for burning at burner surfaces
25 76. Valves 19 comprise manually operable valves
26 coupled with thermocouples 167 which extend through
27 front wall 4 and are located about 0. 75 inches above
28 reverberation screens 115. A valve 19 is associated
29 with each plenum chamber 45, so that plenum chambers
30 45 can be operated independently Or one another.
31 Until thermocouple 167 senses a flame above burner
32 surface 76, valve 19 must be held open manually. When
33 valve 19 is held open, gas flows through tiles 74 to
34 burner surfaces 76 where is it ignited by the flames
35 at ports 155. If the flame above a burner surface 76
36 is extinguished, as by a gust of wind, thermostat 167
37 turns off valve 19 associated with that burner surface
38 76. Burner system 150 can be operated independently
39 of, or in addition to, burner plates 72.
1'~77~7~
1 l`n an alternative embodiment, thermocouples
2 167 are carried by rear wall 5 about 0.75 inches above
3 reverberation screens 115. Each thermocouple 167 is
4 located to sense a flame from either tiles 74 or
burner system 150. If no flame is present adjacent to
6 one of the burner surfaces 76, either from ignition of
7 gas flowing through tiles 74 or from ignition of gas
8 flowing through ports 155, valve 19 which supplies gas
9 to that burner surface 76 is rendered inoperable by
thermocouple 167. Consequently, gas cannot be
11 supplied to a plenum 45 unless either third burner 150
12 is in operation or gas flowing through plenum 45 is
13 being burned at burner surface 76. If the flame at
14 burner surface 76 is extinguished, as by a gust of
wind, the valve supplying gas to that burner surface
16 76 will close unless third burner 150 is in
17 operation. In the latter case, thermocouple 167 would
18 sense the flame from third burner 150 and keep valve
19 19 open.
The parts of the barbecue grill of this
21 invention can be made of any conventional or
22 conveniently available mater$als. It is preferred
23 that container 1 and cover 2 be made of cast aluminum,
24 that grid 12 be made of cast iron or cast aluminum,
that spacers 79 be made of stainless steel, and that
26 rods 100 be made of drawn steel. It is preferred that
27 jet 20 be made of brass. Except as noted, it is
28 preferred that all other parts discussed above be made
29 of aluminized sheet steel of 18 or 20 gauge.
The preferred embodiment described above is
31 illustrative of, and not exclusively definitive of,
32 the barbecue grill of this invention. It is obvious
33 that many variations to the above described embodiment
34 may occur to one skilled in the art, and that those
variations fail within the intent and scope of the
36 invention and the claims set forth below.
29
