Abstract:
The cooking assembly directs initial hot gases from a heat source against a heat semiconductive base. It then guides the gases to flues behind partitions that define sides of a cooking chamber. The gases flow over the partitions, down past food to be cooked, and then out vents. A uniform temperature distribution is achieved in the cooking chamber. The cooking assembly can be a barbecue cooker.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to cooking devices and, more particularly, to portable cooking assemblies for use with external heating means. 
     2. Description of the Prior Art 
     U.S. Pat. Nos. 1,342,455; 2,920,615 and 3,270,740 disclose portable oven devices wherein hot gases flow beneath and around food items to be heated and then out side or upper vent outlets. Particularly with respect to external heat sources, it is detrimental to permit gases at their hottest temperature to make initial contact with the food items. This creates uneven cooking, possible charring and drying of the item. It is also an inefficient use of the heating means. 
     The camp stove toaster of U.S. Pat. No. 3,266,483 seeks to overcome the above problems by providing a cooking chamber that is heated entirely by indirect conductive heat. A U-shaped double walled housing is used to form a passageway for hot gases from a heat source. Again, however, the chamber bottom gets the hottest gases and the top portion the coolest. This sets up a significant temperature gradient and results in uneven cooking. Also, no means are provided to circulate air in an attempt to more evenly distribute the air temperature. 
     U.S. Pat. No. 3,035,568 discloses a portable oven which also relies on indirect conduction heating. Heat applied to a base plate flows by conduction and radiation to an offset cooking platform. The platform has dimpled edges and is spaced from the oven cover to allow convention air to rise from the base plate past the platform. No exhaust vents are provided nor are any air deflectors used to create a uniformity of temperature. As such, there is virtually no control over the temperature surrounding the platform. Also, the platform itself may become unnecessarily hot relative to the ambient air. Especially when covered by a food item. 
     SUMMARY OF THE INVENTION 
     The cooking assembly of the present invention directs initial hot gases from a heat source against a heat semi-conductive base. It then guides the gases to flues behind partitions that define the sides of a cooking chamber. The gases flow over the partitions and downwardly past a food item in the chamber. They exhaust through lower level vent means. Having upper level gas inlets and lower outlets provide for natural continuous flow of heated air by convection. Such flow insures a uniform temperature distribution within the cooking chamber and avoids the initial impact of hot gases direct from the heat source. 
     The heat semi-conductive base serves to deflect the initial hot gas flow to the flues while also distributing the heat therefrom by conduction. With the above heat transfer mechanisms, the cooking chamber performs in a highly efficient manner and thereby conserves energy. It also provides a superior cooking environment by having a controllable and uniform temperature distribution throughout the chamber. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of a portable cooking device constructed in accordance with the present invention. 
     FIG. 2 is a front elevational view of the device shown in FIG. 1 positioned upon a gas barbecue unit shown in phantom. 
     FIG. 3 is a cross-sectional view taken along lines 3--3 of FIG. 2. 
     FIG. 4 is a cross-sectional view taken along lines 4--4 of FIG. 1. 
     FIG. 5 is a cross-sectional view taken along lines 5--5 of FIG. 1. 
     FIG. 6 is an exploded front perspective view of the device of FIG. 1. 
     FIG. 7 is an enlarged fragmentary cross-sectional view of an alternative enclosure showing adjustable side walls and back wall vents. 
     FIG. 8 is a perspective view of an alternative interior cooking assembly for use within a barbecue unit shown in phantom. 
     FIG. 9 is a cross-sectional view taken along lines 9--9 of FIG. 8. 
     FIG. 10 is a perspective view of an interior cooking assembly similar to that shown in FIG. 1. 
     FIG. 11 is a fragmentary cross-sectional view of an alternative enclosure showing an adjustable side wall baffle means. 
     FIG. 12 is a bottom plan view taken along lines 12--12 of FIG. 11. 
     FIG. 13 is an enlarged cross-sectional view taken along lines 13--13 of FIG. 12. 
     FIG. 14 is a perspective view of another alternative interior cooking assembly with a back partition. 
     FIG. 15 is a cross-sectional view taken along lines 15--15 of FIG. 14. 
     FIG. 16 is a cross-sectional view taken along lines 16--16 of FIG. 15 set within a barbecue unit shown in phantom. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference now to FIGS. 1-6 of the drawings, an illustrative embodiment of the invention is shown by numeral 10. An enclosure 12 is provided having a thin-walled flat surfaced structure constructed of metal such as porcelain steel or aluminum. It is characterized by front wall 14 and back wall 16 which are connected by opposing side walls 18. The walls incline upwardly from a bottom peripheral edge 20 and merge with a top wall 22. 
     The front wall may include an optional door and/or glass viewing means 13. As shown, a glass door 15 is used over front wall opening 17. The door pivots about hinges 19,19 with handle 21 and permits easy access to the enclosure interior. 
     A function of the enclosure is to capture hot gases from an external heat source. It is contemplated that a likely source would be the heating means F of a conventional gas barbecue unit common to most households. As such, peripheral bottom edge 20 most preferably defines an open bottom that will overlie and cover at least a major portion of the barbecue housing open top. Since most barbecue housings have a rectangular-shaped open top, bottom edge 20 should likewise define a rectangular-shaped open bottom. Other shapes may also be used. 
     With reference to FIG. 2, it is expected that enclosure bottom edge 20 will rest upon grating G which is set over the open top of housing H of a typical gas barbecue unit. The interior cooking assembly, shown generally by reference 23, will also be supported by the grating. The barbecue housing and enclosure cooperate to entirely enclose the assembly during the cooking operation. 
     The interior cooking assembly illustrated in FIGS. 1-6 and 10 comprises a base 34 having a partition 24 upstanding from each opposing end thereof. The base length is less than the enclosure length to provide open flue areas 26 between each partition and respective side wall. Base width would approximate the enclosure width so that most all hot gases from the underlying heat source F will be deflected into the flue areas. 
     Base 34 is constructed of material that is only semi-conductive of heat. This inhibits localized hot spotting from the underlying heat source. Thickened plates of marble or ceramic material are preferred because they also provide a durable non-oxidizing surface suitable for direct contact with food items such as pizza crusts. 
     Partitions 24,24 are preferably coextensive with the base width and span the enclosure between front wall 14 and back wall 16. It is desirable to center the base over barbecue housing H so that the partitions are equidistant from respective side walls 18,18. In this way, the flue areas will be equal and permit a balanced flow of hot gases about both sides of the enclosure. 
     As shown in the FIGS. 1-6 embodiment, the partitions may include opposing side flanges 27,27. These help facilitate partition juncture with the front and back walls. Such juncture may be a fixed attachment whereby assembly 23 will be part of the enclosure. Alternatively, the interior assembly may be a separate entity for use with a separate enclosure or within existing barbecue cover and housing units as shown in FIGS. 8-10 and 14-16. In such case, the partitions may be without side flanges 27,27 as depicted in FIG. 10. 
     Each partition terminates at an upper edge 25. The upper edges are spaced-apart from top wall 22 a predetermined distance to form open areas. Such areas function as hot gas inlets 28 to direct gases from the flues into a cooking chamber 36. The cooking chamber is defined as the area above base 34 between the partitions and between the front and back walls. 
     The lower portion of each partition further includes a base support means shown as inwardly directed base flange 29. In the simplest construction, opposing ends of base 34 will rest by gravity upon a respective base flange of each partition. Optionally, the base support means may include a clamping device or permanent attachment means such as bolt fasteners. In this way the partition and base would be a unitary assembly. 
     Also located in the lower portion of each partition are vent means shown as a cool gas outlet 30. The outlet is adjacent base 34 and functions to permit cooled gases to exhaust the cooking chamber. In the FIGS. 1-6 embodiment, ducts 31 are used to carry the gases across the open flue areas to an enclosure outlet 32. 
     As best seen by the arrows in FIG. 4, the above-described cooking assembly provides for convection flow of hot gases over the food item P being cooked. The gases cool and become denser as they flow through the chamber and across the item. The outlets, being located adjacent base 34, allow the lower cooled gases to exit the chamber to create a natural circulatory gas flow. 
     Simultaneous with the above convection flow, the heat semi-conductive nature of base 34 readily deflects the underflow of hot gases while slowly conducting only a portion of the gaseous thermal energy. The resultant temperature gradient across the base thickness is significant and functions to eliminate unwanted hot spots at the base cooking surface. It does allow, however, the attainment of an effective base surface cooking temperature. This is especially advantageous for foodstuffs with crusts such as pizzas. With the above system, hot gases continuously flow over the pizza top to melt the cheese particles while a cooler base surface allows for cooking of the underlying crust without burning or dryness. 
     The invention contemplates variations of the enclosure and also the interior cooking assembly to accomodate different sizes and models of barbecue units. It has been found that most commonly available barbecue units vary in length (side wall to side wall) rather than width. As such, FIG. 7 illustrates enclosure 12&#39; which has wall adjustment means shown as adjustable side walls 18&#39;. Side wall slot and wingnut combinations 39 allow the side walls to move in or out, as shown by arrows A, to overlie different lengths of barbecue housings. With the above variation, vent means shown as exhaust outlets 41 may be used in place of the vent ducts. Such outlets extend through back wall 16&#39; adjacent base 34. 
     Alternatively, FIGS. 11-13 illustrate a different wall adjustment means shown as sliding baffle 44. The baffle is used to overlie portions of a barbecue grate not covered by the enclosure. In this embodiment, fasteners 45 extend through baffle slots 46 and adjustably secure the baffle to spaced-apart bosses 47 on side wall 18. The baffles may be on either or both of the opposing side walls. They move laterally as shown by arrows B in FIG. 13 to prevent heat loss and deflect the hot gases into the flues 26. 
     Although not specifically shown, it will be appreciated that both of the above-described wall adjustment means could be used with back wall 16. This would allow the enclosure to accommodate variations in barbecue width. 
     With reference to FIGS. 8 and 9, a modified interior cooking assembly 23&#39; is illustrated for use with barbecue units having a profiled housing H&#39;. As shown, such housings typically include an open top with a front cut-out portion 50. Enclosures 12&#34; for the above housings commonly have back wall vent systems shown as offset vent opening 52. To position the base adjacent the vent opening, a rear lip flange 54 is used to support the base back end portion on the barbecue housing back edge. 
     A front pedestal flange 56 supports the base front end portion upon grating G. The pedestal flange has sufficient height to support the base in a level manner between partitions 24&#39;. For convenience, the partitions may include handle means shown as hand openings 58. 
     To facilitate an even distribution of hot gases and a controlled exit of cooled gases, a back partition 60 may be used. The back partition connects with side partitions 24&#39; to form a 3-sided cooking chamber 36. It includes exhaust outlets 41&#39; which are adjacent base 34. The outlets communicate with the offset vent opening 52 for exiting the cooled gases in a natural convection fashion. 
     FIGS. 14-16 illustrate a cooking assembly 23&#34; similar to the FIGS. 8-9 embodiment, but with additional venting means. Base 34 is supported horizontally by rear lip flange 54&#39; and front pedestal flange 56&#39;. As before, the lip flange engages the housing back edge and the pedestal flange is supported by grating G. The back partition 60&#39; forms a 3-sided cooking chamber with side partitions 24&#34;. 
     The venting means include exhaust outlets 41&#34; which extend through the back partition and communicate with offset vent opening 52&#39; of enclosure 12&#39;&#34;. The side partitions also include venting means shown as vent apertures 62. Such apertures extend through the lower portion of each side partition adjacent the base. They open into a side duct 64 which overlies the apertures on the outside of each partition. 
     The ducts form enclosed passageways which communicate with vent openings 52&#39; for exhausting the cooled gases from cooking chamber 36. The above arrangement may be useful for larger capacity cooking assemblies or where greater circulation of gases are desired. Of course in the above and all other embodiments, temperature and gas flow is also controllable by regulation of the heat source. 
     While the invention has been described with respect to preferred embodiments, it will be apparent to those skilled in the art that various modifications and improvements may be made without departing from the scope and spirit of the invention. Accordingly, it is to be understood that the invention is not to be limited by the specific illustrative embodiments, but only by the scope of the appended claims.