AIR SLOT COOKING GRILL
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a food preparation apparatus and more particularly to a high velocity air slot device for grilling or cooking food.
Description of the Prior Art
Foods, especially meat sections, are desirably grilled upon an open surface over a high temperature heat source such as heating elements, charcoal briquets, gas bur- ners or even open flames. Grilling gives the food an unique combination of texture, flavor, odor and appearance and in particular provides flavor enhancement by browning portions of the food in contact with the grill. The browning of the food involves a complex carmelizing process which takes place on the surface of the food. The carmelizing process involves the nature of the food and its juices and moisture, and is largely responsible for the unique "charcoal grill" flavoring imparted to the food being grilled.
Conventional grills include a grill to cook and support food products. The grill is located above a heat source, such as those mentioned above, which is contained in a cavity directly below the grill. The heat source of such grills operates at very high temperatures up to and including the temperature of burning charcoal, open gas flame tips or cherry red electrical elements. To cook the food products supported on the grill such devices depend, to a large extent, upon direct heat transfer through radiation 0 together with some convection heating through the air and some conduction heating through the grill surface which results from a combination of radiation heat transfer and convection heating. After grilling, the food product bears an imprint of the grill work pattern on its surface which are carmelized portions of high flavor enhancement resulting from contact with the grill.
Conventional grills usually do not possess means ■ for temperature regulation, but instead operate at unregu¬ lated high temperatures in order to sear and cook rapidly, rather than bake, the food product being grilled. The high operating temperatures of such grills are frequently above the ignition point of grease which accumulates along with food juices and moisture, and drips onto the heat source causing undesired flames and smoke. Some conventional grills have means to control energy input and consequently the temperature of the heat source. In such devices the speed of cooking can be controlled, and smoke and flames caused by burning grease can be minimized. This is generally a unsatisfactory approach, however, since reducing the temperature of the heat source drastically reduces the amount of heat that can be transferred to the food. Specifically, reducing the tem¬ perature of the heat source diminishes the effect of radiation heat transfer and leaves a grill operator with only relatively inefficient convection heating to cook the food.
Other conventional grills employ blowers and plenum
chambers to force air past a heat source and improve heat transfer efficiency by artificial movement of air from a heat source to a food product. After the air is forced past the food product, however, it is generally exhausted to the atmosphere and heat is therefore inefficiently applied to the food. Furthermore, such grills usually have commercial rather than domestic application, are generally large and heavy, and do not provide truly appetizing charcoal flavor to the food unless they employ essentially an open "fire" below the grates.
SUMMARY OF THE INVENTION
The present invention is directed to an air slot cooking device that avoids the above-mentioned disadvantages which are characteristic of the prior art. More specifi- cally, the air slot cooking device of the present invention is a recirculating hot air system for grilling and cooking food products. The system has high heat transfer effi¬ ciency, reduces the time required to cook food products over that required by conventional grilling devices and provides foods having enhanced moisture retention.
The air slot cooking device of the present inven¬ tion is formed from an enclosure having a bottom, side walls and a removable top. The enclosure defines a chamber having an air- flow opening and an air passage opening. A housing abuts a side wall of the enclosure. The housing communicates fluidly with the chamber through the air flow opening. A blower is disposed within the housing. The blower circulates air through the system and has air input means and air output means. The air input means of the blower is in fluid communication with the chamber through the air flow opening. The air output means of the blower is in fluid communication with the chamber through the air passage opening.
A grill having a high percentage of open area is disposed within the enclosure and divides the chamber into an operating space and a heat supplying space. The air flow
opening is located in the operating space of the enclosure and the air passage opening is located in the heat supplying space of the enclosure.
A heat supplying element is disposed within the enclosure and is located in the heat supplying space. A jet curtain plate having an array of air slot openings is disposed within the enclosure and is located between the grill and the heat supplying element. Preferably, a heat transfer plate is disposed within the enclosure and is, pre- ferably, located between the heat supplying element and the jet curtain plate.
In operation, air from the output means of the blower enters the enclosure through the air passage opening. The air is turbulized as it passes across and scrubs heat from the heat supplying element. The air is then directed to the array of air slot openings in the jet curtain plate. The air emanates as jets of air through the array of air slot openings in the jet curtain plate and is directed toward the grill. The air exits the enclosure through the air flow opening, enters the input means of the blower and is recirculated through the system.
The air slot cooking device of the present inven¬ tion may be modified to have any shape enclosure, to include additional jet curtain plates or may be adapted for use in an existing grill.
The air slot cooking device of the present inven¬ tion is preferably, a cooking device utilizing recirculating high velocity hot air in which the air is heated to tem¬ peratures of approximately 300°F or higher and circulated at rates of approximately 300 feet per minute or higher.
BRIEF DESCRIPTION OF THE DRAWINGS
In describing the present invention, reference will be made to the accompanying drawings in which:
Figure 1 is a perspective view of the air slot cooking grill of the present invention;
Figure 2 is a longitudinal sectional view taken
along line 2-2 of Fig. 1;
Figure 3 is a transverse sectional view taken along line 3-3 of Fig. 1;
Figure 4 is a longitudinal sectional view similar 5 to Fig. 2 of an alternate embodiment of the present inven¬ tion;
Figure 5 is a detail sectional view taken along line 5-5 of Fig. 4;
Figure 6 is a longitudinal sectional view similar 10 to Fig. 2 of an alternate embodiment of the present inven¬ tion;
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, and in particular Figure 1, an air slot cooking grill generally indicated at
1510 includes a recirculating hot air system in an enclosure 12. The enclosure 12 has a* base and side walls defining a chamber. The chamber preferably has a rectangular con¬ figuration but may be of any configuration desired. The enclosure 12 is abutted by a housing 14. As shown in Figure
202, a gasket 60 may be disposed between the housing 14 and the enclosure 12 to prevent air from escaping from the system.
A grill 16 to support food for cooking is disposed above the base and within the enclosure 12. The grill 16
25 rests upon and is supported by a flange 40. The grill 16 extends to all side walls of the enclosure chamber and divi¬ des the enclosure chamber into an operating space above the grill 16 and a heat supplying space below the grill 16. As shown in Figure 2, an air flow opening 30 in the housing 14
30 communicates fluidly with the operating space of the enclo¬ sure 12 so that air from the operating space can pass into the housing 14. The air flow opening 30 may be adjusted by a control device 34 such as a flapper or gate to regulate the amount of air flowing through the air flow opening 30.
35 The control device 34 may be adjusted by a handle 36.
The housing 14 defines a plenum chamber 15 and
includes a blower 26 for circulating heated air. The blower 26 has air input means and air output means. The input means of the blower 26 is in fluid communication with the operating space of the enclosure through the air flow opening 30. The output of the blower 26 is attached to a transfer connection 42 which passes through an air passage opening 32 in the housing 14 and enters the heat supplying space of the enclosure chamber. By operating the blower 26, air can be circulated from the enclosure chamber operating space into the housing 14, through the blower 26 and transfer connection 42, and back into the heat supplying space of the enclosure chamber.
A heat supplying element 18 is mounted in the heat supplying space and above the base of the enclosure chamber. The heat supplying element 18 is supported on the base by a plurality of supports 88. The heat supplying element may be supplied with, energy from an external source such as through cord 17. The heat supplying element 18 extends over a con¬ siderable portion of the base and particularly toward the transfer connection 42.
A heat transfer plate 20 may optionally be disposed in the heat supplying space of the enclosure chamber spaced apart and above the heat supplying element 18. If included, the heat transfer plate 20 defines a turbulized air control space containing the heat supplying element 18 and located between the base of the enclosure and the heat transfer plate 20. If included, the heat transfer plate 20 also defines an air transfer passage 82 adjacent a side of the enclosure opposite the air flow opening 30 and the transfer connection 42. If included, the heat transfer plate 20 pre¬ vents air from entering the operating space of the enclosure chamber except through the air transfer passage 82. If the heat transfer plate 20 is included, when the blower 26 is operated, air enters the enclosure 12 through the transfer connection 42 and below the heat transfer plate 20 and moves through the heat supplying space to the air transfer passage 82 defined by the heat transfer plate 20.
A jet curtain plate 22 is mounted in the heat supplying space of the enclosure chamber and is spaced apart and above the heat supplying element 18, as well as heat transfer plate 20 if included. The jet curtain plate 22 rests upon and is supported by a flange 38. The jet curtain plate 22 extends to all side walls of the enclosure chamber and defines a turbulized air control space between the heat supplying element 18 or heat transfer plate 20 and the jet curtain plate 22. The jet curtain plate 22 contains an array of slots 24 through which turbulized air from the tur¬ bulized air control space is unturbulized and directed in a series of jet streams toward food supported on the grill 16. The slots 24 of the jet curtain plate 22 vary in width, length and number in relation to the horsepower of the blower to yield jets of air emanating from the slots 24 at a velocity of from 300 to 4000 feet/minute and preferably from 300 to 1700 feet/minute. The.velocity of air emanating from the slots 24 may be measured by a Dwyer Air Velocity Calculator: #460 Air Meter made by Dwyer Instruments, Inc., Michigan City, Indiana under U.S. Patent No. 2,993,374. When a 1/25 horsepower, 3400 RPM, squirrel cage blower with a 7.31 square inch nozzle was used, 66 slots totalling 20.46 square inches of slot area yielded an adequate velo¬ city of air emanating from the slots. The slots 24 may be varied in size to yield streams of air having different velocities at different areas of the jet curtain plate 22. Such an arrangement provides areas in the grill having dif¬ ferent cooking speeds. The jet curtain plate 22 distributes heat uniformly and efficiently to the surface of the food being cooked across the entire surface area of the grill 16. The unturbulized air emanating from the slots 24 of the jet curtain plate 22 travels toward the operating space of the enclosure chamber where it can be circulated back through the housing 14 and blower 26 to again enter the heat supplying space of the enclosure chamber. When the blower 26 is operating, a continuous stream of air flows through the entire system. Turbulized air from the blower 26 scrubs
the heat supplying element 18 and picks up heat which is then delivered to the food by the high velocity jets of air emanating from the slots 24 of the jet curtain plate 22.
The jet curtain plate 22 is uniquely corrugated in a pattern of rounded v-shaped corrugations alternately v- shaped and inverted v-shaped. As shown in Figure 3, the slots 24 of the jet curtain plate 22 are disposed in the crests rather than the troughs of the v-shaped corrugations. In operation, high velocity air emanating from the slots 24 of the jet curtain plate 22 heats the food and tends to prevent grease from dripping through the slots 24 into the heat supplying space. Instead, grease drips into the troughs between the slots 24. Preferably, the jet cur- tain plate 22 is inclined at a slight angle from the hori¬ zontal, as shown in Figure 2, so that the grease in the troughs runs to one side of the jet curtain plate 22 where it can drop downwardly toward the heat supplying space into a collecting area 50. Those skilled in the art will recognize that holes may be provided in the downwardly inclined end of the jet curtain plate 22 to aid in the remo¬ val of grease from the jet curtain plate 22. The collecting area 50 may preferably be defined by a dam member 52 disposed on the rectangular base of the enclosure in an end portion of the heat supplying space. A drain 54 may be pro¬ vided in the collecting area 50 to remove accumulated grease. Those skilled in the art will recognize that any collecting member that can withstand hot grease such as a metal tray may be disposed in the collecting area 50. Grease dripping from the jet curtain plate 22 is effectively prevented from contacting the heat supplying element 18 since the heat supplying element 18 does not extend into the collecting area 50 of the enclosure. Thus the apparatus of the present invention greatly reduces or eliminates flame- ups, excessive smoke or off flavor that would result from grease contacting a high temperature heat supplying element. Smoking and flaming of grease drippings is effectively pre-
vented by the present apparatus because the grease drippings are collected and prevented from falling on the heat supplying element 18. Even if some grease falls through the slots 24 onto the heat supplying element 18, the jet curtain plate 22 acts as a flame barrier so that rising flames from burning grease cannot reach the food being cooked where it could cause damage to the food or add the bitter flavor of burned grease.
If included, the heat transfer plate 20 adds to the efficient transfer of heat from the heat supplying element 18 to the moving air. The heat transfer plate 20 collects heat from radiation and convection heat transfer and trans¬ fers this heat to the moving air which is thus more uni¬ formly heated before passing upward through the slots 24 of the jet curtain plate 22.
Also, the extreme efficiency of jets of high velo¬ city heated air emanating from the slots 24 of the jet cur¬ tain plate 22 speeds the cooking of ttøe food supported on the grill without requiring an extreme differential between the temperature of the heat supplying element and the tem¬ perature of the air. Unused heat contained in the recir¬ culating air is conserved by the apparatus of the present invention which may be insulated _o reduce heat loss. It is therefore possible to provide quick efficient cooking of food with air heated to about 300°-500°F and preferably to about 400° - 500°F without requiring the heat supplying ele¬ ment 18 to run at full capacity, which conserves energy and reduces the tendency of grease that does manage to contact the heat supplying element 18 to smoke and flame. The enclosure 12 is also provided with a removable top. The removable top is preferably an access cover 28 as shown in Figures 1 and 2. The access cover 28 is openable into the operating space of the enclosure to provide access to the grill 16. The access cover 28 may constitute a por- tion of the enclosure located above the grill 16 and pre¬ ferably constitutes the entire top section of the enclosure 12. Also, the access cover is preferably attached to the
housing by a hinge 56 so the cover may be raised in order to provide access to the grill 16. A gasket 58 may be disposed between the housing 14 and the access cover 28 to prevent heated air from escaping from the enclosure 12. Most pre- ferably, insulation 46, a handle 48 and a viewing port (not shown) are provided on the access cover 28 for convenience. Those skilled in the art will recognize that any type of access cover that will provide access to the grill 16 may be utilized in the present invention. The above-described air slot cooking grill may rest upon a support surface 64 and be spaced from the support surface by a plurality of spacer legs 62.
A preferred embodiment of the present invention similar to the embodiment described above, is shown in Figures 2 and 3. In this embodiment, a second jet curtain plate 22' is mounted in the heat supplying space of the enclosure chamber and is spaced apart from and between the first jet curtain plate 22 and the grill 16. The second jet curtain plate 22' is spaced from the first jet curtain plate 22 by a plurality of supports 44. The second jet curtain plate 22* has an array of slots 24• similar to the array of slots 24 in the first jet curtain plate 22. The slots 24' are staggered with the slots 24 of the first jet curtain plate, as shown in Figure 3, to provide a lateral offset between the slots of the two jet curtain plates 22 and 22'. The slots 24' of the second jet curtain plate 22* may also be offset longitudinally with the slots 24 of the first jet curtain plate 22. A turbulized air control space is created between the first jet curtain plate 22 and the second jet curtain plate 22'. The second jet curtain plate 22* is nearest the grill 16 and ultimately the recirculating air reaches the grill 16 through the slots 24' of the second jet curtain plate 22'. Preferably, both jet curtain plates 22 and 22' are inclined slightly at an angle from the horizon- tal so that grease drippings can run off from either plate to the previously defined collecting area 50.
The second jet curtain plate 22' is added to the
apparatus to obtain better mixing of the heated air. Specifically, as heated air passes through the slots 24 of the first jet curtain plate 22 into the turbulized air control space it is required to shift laterally or longitu-
5 dinally to finally emanate through the slots 24' of the second jet curtain plate 22* as an unturbulized jet stream into the operating space of the enclosure chamber. This staggered slot arrangement requires that any grease dripping through a slot 24' of the second jet curtain plate 22'
10 necessarily falls onto an unslotted trough of the first jet curtain plate 22 and then is diverted to the collection area 50. Thus, the staggered slot arrangement totally eliminates the possibility of grease dripping downwardly into the heat supplying space and onto the heat supplying element 18.
15 An alternate embodiment of the present invention is shown in Figures 4 and 5. In this embodiment, a jet curtain plate 22" is located in the operating space of the enclosure chamber above the grill 16 and spaced apart downwardly from the removable top 28 of the enclosure. The first jet cur-
20 tain plate 22 or the first and second jet curtain plates 22 and 22' and the grill 16 may all be coextensively shortened, compared to the embodiments shown in Figures 2 and 3, at an end opposite the housing 14. The jet curtain plate 22 or plates 22 and 22' below the grill 16 and the jet curtain
25 plate 22" above the grill may be mounted at the side of the enclosure chamber opposite the shortened ends. A wall member 74 having a diverter 70 at one end thereof may be disposed within the enclosure and may be located across the shortened ends of the jet curtain plate 22 or plates 22 and
3022' and the grill 16. The wall member 74 extends upward to the jet curtain plate 22" and defines an air column space 72 between the wall member 74 and the enclosure 12. The air column space 72 communicates fluidly with the heat supplying space, and a top air control space located between the jet
35 curtain plate 22" and the enclosure 12.
When air is circulated by the blower 26 into the heat supplying space it passes across the heat supplying
element 18 and if the heat transfer plate 20 is included, enters the air transfer passage 82. A first portion of the air is diverted by the diverter 70 into the air control space or spaces between the jet curtain plate 22 or plates 22 and 22' and the grill 16, and a second portion of the air is diverted by the diverter 70 upwardly through the air column space 72 into the top air control space between jet curtain plate 22" and the enclosure 12. Unturbulized jet streams of air are thus directed toward the top and bottom surfaces of the grill 16. This arrangement provides for very fast cooking since additional heat is transferred to food placed on the grill by the additional impingement of high velocity air from jet curtain plate 22". Dead air spa¬ ces are scrubbed away by the high velocity air and mixing of the opposing air jets around the edges of the food being cooked which improves heat transfer and results in still faster cooking.
Those skilled in the art will recognize that the diverter 70 may be replaced by one or more chimneys located adjacent any side wall of the enclosure 12. Such chimney or chimneys being in fluid communication with the heat supplying space and the top air control space.
The above-described alternate embodiment of the present invention may be further modified by providing a grid 66 of generally flat configuration having its edges spaced apart a non-interfering distance from the side walls of the enclosure. The grid 66 is flexibly hung below jet curtain plate 22" by supports 68, such as knee hinge sup¬ ports, which permit relative movement of the grid 66 in a vertical direction. The grid 66 is spaced apart above the grill 16 and is adjustably positioned within the flexible adjustment range of the supports 68 to rest upon the surface of food being cooked. The grid 66 may be retained by a catch 76 when not in use. Jet curtain plate 22", grid 66 and supports 68 are preferably attached to the access cover 28 and are accordingly raised upwardly when the cover is opened. When hot air is circulated in the enclosure 12, the
grid 66 is heated in a similar manner as the grill 16 and provides the same effect upon the surface of the food being cooked as the grill 16 such as the familiar grid pattern as well as the carmelized flavor enhancing areas. The grid 66 also aids in the efficient transfer of heat to the food being cooked thus contributing to both enhanced flavor and cooking speed. Because the food product is cooked from the top and bottom and has flavor enhancing carmelized areas on both surfaces, this embodiment of the present invention 0 allows uniform cooking of the food without requiring the food to be turned.
Another embodiment of the present invention as shown in Figure 6, is a modified grill for a retrofit appli¬ cation which retains many of the advantages of the above- described embodiments, but does not contain all of the elements. The retrofit application may be used with a cer¬ tain class of domestic type cooking ranges generally known as "Jenn-Air" ranges. Such ranges have a built-in grill portion consisting of a surface (not shown) and a sunken 0 area 80 located below the surface. The sunken area 80 con¬ tains respectively upward from the bottom, a grease collecting plate 78 having a plurality of openings for grease drippings to run through and collect on the bottom of the sunken area 80, a horizontally disposed heating element 584 having snaked s-shaped curves separated by straight por¬ tions, and a grill surface (not shown). A separately located suction apparatus (not shown) draws smoke away from the grill. The purpose of such grills is to permit indoor grilling without generating excessive smoke. Q The alternate retrofit embodiment of the present invention utilizes the sunken area 80, the grease collecting plate 78 and the heat supplying element 84 of a previously existing indoor grill. The existing grill surface, however, is removed and replaced with a slightly inclined jet curtain 5 plate 22 as described above. The jet curtain plate 22 extends across the area of the existing unit and a grill 16 is located over the sunken area 80 and is spaced apart above
the jet curtain plate 22. Part of the grill 16 and jet cur¬ tain plate 22 are cut away at one end and the cut away por¬ tion is occupied by a modified air transfer connection 42 extending above the surface of the grill 16 into a housing 14 and connected to a blower 26 of the type described above. The housing 14 abuts a modified enclosure 12 and is in fluid communication with the modified enclosure 12 through air flow opening 30. The modified enclosure 12 forms an operating space above the grill 16, has edges adapted to fit sealingly around the sunken area 80 at the level of the grill 16 and is completely open on the grill side.
This alternate retrofit embodiment functions in a manner similar to the above-described embodiments in that air is circulated by the blower 26 into a heat supplying area in a turbulent fashion through the modified air transfer connection 42, the heated air emanates as high velocity air streams toward the grill 16 through an array of slots in the jet curtain plate 22, the air impinges upon and cooks food placed on the grill 16, and the air is then recirculated. The jet curtain plate 22 performs its func¬ tion of collecting and transporting grease drippings to one end of the sunken area 80 instead of allowing it to drip onto the heat supplying element 84. Thus, this alternate retrofit embodiment of the present invention significantly eliminates smoke and flaming problems of the existing units as well as greatly increasing the cooking rate because of the high velocity air directed toward the food. The auxi¬ liary smoke removal portion of the existing units is not required in the retrofit application. The entire retrofit assembly including the housing 14, blower 26, air transfer connection 42 and enclosure 12 are plug-in units and are freely removable from the modified grill.
All of the above-described embodiments of the pre¬ sent invention are suitable for indoor use since they completely enclose the food being grilled and recirculate the air internally.
While preferred embodiments of the present inven-
tion have been shown and described, it will be understood by persons skilled in this art that various changes and modifi¬ cations may be made therein without departing from the spirit and scope thereof as defined by the following claims.