CA1277879C - Barbecue grill - Google Patents

Abstract

Abstract This invention relates to a barbecue grill, and in particular to a high pressure gas fired barbecue grill having perforated ceramic heating elements which emit infrared radiation. A pair of steel rods are suspended in a cast aluminum housing, and a pair of plenum chambers are suspended therebetween. The upper surfaces of each plenum chamber comprises a pair of perforated rectangular ceramic blocks separated by an imperforate metal plate. The bottom of the housing is open, and has a tray carried proximate the opening for food particles.

Description

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.
~. ~

,, 1 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 1'~77~7'~3 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.

1~77~79 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.

1'~77~7'~3 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.

1~77~7'3 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 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 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 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 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 1'~77879 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 1~77879 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 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.

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.

Claims (26)

1. In a gas barbecue grill comprising:
(a) a container having upstanding sidewalls forming a cavity having an upper opening, (b) a cover affixed to said container, movable to a closed position to substantially cover said upper opening and movable to an open position, (c) a grid suspended from said upstanding sidewalls proximate said upper opening, having a generally horizontal portion adapted to support food, (d) a heat generating system comprising:
(i) a plenum chamber supported within said cavity below said grid, comprising walls forming a chamber having a top opening and a gas inlet port, the improvement comprising:
(ii) a burner plate supported by said plenum chamber, substantially covering said top opening and comprising at least two spaced tiles of low heat conductivity each having a burner surface and a plurality of holes therethrough adapted to allow the exit of gas from said plenum chamber to said burner surface, said tiles being separated by a spacer which is impervious to the passage of gas therethrough and of high heat conductivity to present a surface which in use of the grill reaches a temperature sufficient to vaporize foods dropping thereon and insufficient to cause spontaneous ignition within the plenum, (iii)means on said burner plate to propagate gas flame between said tiles across said spacer, (iv) a gas inlet duct having a longitudinal axis, having a proximate portion affixed to said plenum chamber and adapted to introduce gas into said plenum chamber through said gas inlet port, having a distal end exterior to said plenum chamber, and having an air inlet opening exterior to said plenum chamber between said proximate end and said distal end, (v) a gas jet affixed to said distal end of said gas inlet duct, having a gas discharge orifice generally on said axis, and (e) means for connecting said gas jets to a source of combustible gas, whereby gas can be introduced to said gas jets and discharged through said orifices into said gas inlet ducts, mixed with air drawn into said ducts through said air inlet openings to create a gas-air mixture, said mixture being introduced into said plenum chambers and further mixed to create an intimate gas-air mixture, said intimate mixture being forced through said holes in the spaced tiles of said burner plates and burned proximate said burner surfaces to create heat and infrared radiation suitable for cooking food disposed on said grid.

2. The barbecue grill of claim 1 wherein the tiles of the plenum chamber comprise two ceramic tiles each having a generally rectangular burner surface of generally equal size, said spacer comprising a metal sheet, and each of said tiles having from about 100 to about 400 holes per square inch of burner surface area, calculated by perimeter measurements.

3. The barbecue grill of claim 2 wherein the ratio of the total burner surface area of said tiles to the total surface area of said grid is from about 1:2 to about 1:4, said surface areas calculated by perimeter measurements.

4. The barbecue grill of claim 3 wherein said burner plates are spaced from said sidewalls and from one another, said top openings are of generally rectangular configuration, and said tiles are spaced apart such that together said burner surfaces form a generally rectangular generally horizontal pattern, the total area of said burner surfaces of said tiles comprising from about 50% to about 90% of the total surface area of said pattern, said areas calculated by perimeter measurements.

5. The barbecue grill of claim 4 wherein each of said plenum chambers carries a first tile and a second tile, said burner surfaces of said first tiles generally residing in a first plane and said burner surfaces of said second tiles generally residing in a second plane, each plane inclined from the horizontal by from about 1 degree to about 5 degrees about a horizontal axis between said first tiles and said second tiles, said tiles residing below a horizontal plane through said axis, such that said first and second tile burner surfaces are inclined away from one another.

6. The barbecue grill of claim 4 wherein said plenum chamber has generally trapezoidal end walls of generally equal dimensions, generally rectangular side walls of generally equal dimensions, said end walls and said side walls forming a generally rectangular, generally horizontal top opening, and a generally rectangular floor having an area from about 0.25 to about 0.4 times the area of said top opening, one of said end walls having a gas inlet opening therein.

7. The barbecue grill of claim 4 wherein said ducts have generally uniform cross-sectional areas between said proximate ends and said distal ends.

8. The barbecue grill of claim 4 including a pair of rods extending in a generally parallel manner between opposite sidewalls of said container and said plenum chamber walls carry first brackets adapted to engage said rods to suspend said plenum chamber therebetween.

9. The barbecue grill of claim 8 wherein each of said rods has a pair of ends and each of said said sidewalls carries a pair of second brackets each of which is adapted to disengagedly support one of said ends, and wherein said first brackets project from said plenum chamber walls proximate said top opening, such that said plenum chambers and said rods may be conveniently installed and removed from said container.

10. The barbecue grill of claim 9 wherein said sidewalls terminate in a lower edge defining a lower opening, and said sidewalls carry channels proximate said lower opening by which a tray is slidably supported, movable to a first closed position in which said tray substantially covers said lower opening and to an open position in which said tray projects from said container such that it is accessible for cleaning.

11. The barbecue grill of claim 10 wherein said gas is introduced to said gas jet at a pressure of between about twenty inches and bout sixty inches of water.

12. The barbecue grill of claim 1 wherein the spacer comprises a sheet of stainless steel coextensive with the tiles separated thereby and having an upper surface substantially planar therewith.

13. A gas barbecue grill comprising:
(a) a container having upstanding sidewalls comprising a front wall, a back wall, and cast metal sides, forming a cavity of generally rectangular horizontal cross section, said cavity being substantially open at the top and having lower sidewalls terminating in a generally horizontal plane forming a generally rectangular lower opening, (b) a cover attached to said container, movable to a close position to substantially cover said upper opening and movable to an open position, (c) a generally horizontal grid carried by said sidewalls within said cavity proximate said upper opening, adapted to support food, (d) a burner system carried by said sidewalls within said-cavity below said grid, adapted to cook food supported by said grid, comprising a pair of gas inlet ducts, plenum chambers, and burner plates on said plenum chambers, said burner plats having upper surfaces and having a plurality of holes in said upper burner surfaces adapted to allow the exit of gas from said plenum chambers and the burning of said gas proximate said burner surfaces, (e) a tray carried by said container below substantially all of said burner system, adapted to substantially cover said lower opening in a closed position to catch food droppings from said grid, and adapted to be movable to an open position to facilitate removal of said food droppings, (f) means for connecting said gas inlet ducts to a source of combustible gas, (g) a rotisserie burner comprising a tube having a gas inlet opening adapted to be connected to a gas supply and having first perforations adapted to allow gas to flow from said tube and to burn proximate said burner surfaces, and (h) a spark generator and said spark generator and said tube being carried by said back wall, said tube having a generally horizontal longitudinal axis and having a second perforation adapted to discharge gas adjacent to said spark generator and to propagate a flame created by said spark generator to said first perforations.

14. The barbecue grill of claim 13 wherein said tray comprises a slidable drawer.

15. The barbecue grill of claim 14 wherein a pair of parallel generally horizontal channels depend from said lower sidewall proximate said lower opening and said drawer has lateral edges adapted to be received by said channels such that said drawer is suspended below said lower opening in its closed position and is slidable removable for cleaning.

16. The barbecue grill of claim 13 wherein support rods are removably supported between opposite sides of said container, a pair of plenum chambers is supported by said support rods within said cavity spaced from said sidewalls, and said burner plate being carried by each of said plenum chambers comprising a tile of low heat conductivity having a plurality of holes therethrough adapted to allow the exit of gas from said plenum chambers.

17. The barbecue grill of claim 16 wherein said support rods are supported by said sidewalls generally horizontally and each of said burner plates comprise at least two ceramic tiles separated by a plate impervious to th passage of gas, and mens exist on said burner plates to propagate gas between said tiles.

18. The barbecue grill of claim 17 wherein each of said gas inlet ducts has a proximate end connected to one of said plenum chambers and a distal end carrying a gas jet having a gas discharge orifice, said gas inlet ducts having generally uniform cross-sectional areas between said proximate ends and said distal ends.

19. The barbecue grill of claim 13 wherein said second perforation comprises a circumferential slot having a first end adjacent to said spark generator and a second end adjacent to said first perforations.

20. In a gas barbecue grill comprising:
(a) a container having upstanding sidewalls forming a cavity having a generally open upper end.
(b) a grid suspended generally horizontally from said upstanding sidewalls proximate said upper end, adapted to support food for cooking;
the improvement comprising:
(c) a pair of gas inlet ducts having distal ends carrying gas inlet jets and having proximate ends, and means for connecting said-gas jets to a source of pressurized combustible gas, (d) a pair of plenum chambers, each of which has a gas inlet port adapted to receive one of said gas inlet ducts, and each of which plenum chambers has an upper burner plate comprising at least two tiles of low heat conductivity material having upper burner surfaces and a plurality of holes therethrough, and a separator plate interposed between a pair of said at least two tiles and impervious to the passage of gas therethrough, (e) means associated with said burner surfaces to propagate gas flame between said tiles across said separator plate on each of said plenum chambers, (f) said gas inlet ducts having generally uniform cross-sections, (g) said means for connecting said gas jets to a source of combustible gas including a pressure regulating system providing gas to said jets at a pressure of greater than about 20 inches of water, wherein the necessity for modulation of combustion supporting air flow is avoided.

21. The barbecue grill of claim 20 wherein said tiles are spaced from one another and said burner surfaces define a generally rectangular horizontal pattern, and the ratio of th total burner surface area of said tiles to the surface area of said pattern is from about 1:1.2 to about 1:2, calculated by perimeter measurements.

22. The barbecue grill of claim 21 wherein the ratio of the total burner surface are of said tiles to the total surface area of said grid is from about 1:2 to about 1:4, calculated by perimeter measurements.

23. The barbecue grill of claim 20 wherein a third burner is provided, comprising a tube carried by said sidewalls, said tube having a first end adapted to be connected to a gas supply, a closed second end, and an intermediate portion having a front surface proximate said plenum chambers, said front surface having first perforations therein adapted to allow gas to flow from said tube and to be burn proximate said burner surfaces.

24. The barbecue grill of claim 23 wherein a spark generator is located adjacent to said tube, and said tube has a second perforation adjacent to said spark generator adapted to allow sufficient gas therethrough to allow ignition thereof by said spark generator to establish a flame adjacent to said second perforation, said second perforation located circumferentially on said tube between said spark generator and said first perforations and adapted to communicate said flame to said first perforations.

25. The barbecue grill of claim 20 wherein said gas inlet ducts include fixed size air inlets for introduction of combustion supporting air, said air inlets being dimensioned as a function fo the pressure.

26. In a gas barbecue grill comprising:
(a) a container having upstanding sidewalls forming a cavity having an upper opening, (b) a cover affixed to said container, movable to a closed position to substantially cover said upper opening and movable to an open position, (c) a grid suspended from said upstanding sidewalls proximate said upper opening, having a generally horizontal portion adapted to support food, and (d) a heat generating system comprising a plenum chamber supported within said cavity below said grid, comprising walls forming a chamber having a top opening and a gas inlet port, the improvement comprising:

a burner plate supported by said plenum chamber substantially covering said top opening and comprising at least two spaced tiles of low heat conductivity each having a burner surface and a plurality of holes therethrough adapted to allow the exit of gas from said plenum chamber to said burner surface, said tiles being separated by a spacer formed of sheet metal which is impervious to the passage of gas therethrough and of high heat conductivity to present a surface which in use of the grill reaches a temperature sufficient to vaporize foods dropping thereon and insufficient to cause spontaneous ignition of gas within the plenum, and including means associated with said burner plate to propagate gas flame between said tiles across said spacer sheet.