Pellet grill

A cooking grill has a firepot configured to burn pelletized fuel fed from an auger, a cooking grate above the firepot, and a double walled enclosure interposing the firepot and the cooking grate and containing and directing flow of combustion gases from the firepot up to the cooking grate.

FIELD OF THE INVENTION

This disclosure relates to solid fuel cooking in general and, more particularly, to systems for cooking using solid fuel pellets.

BACKGROUND OF THE INVENTION

Outdoor wood pellet fired cooking and smoking appliances are described, for example, in U.S. Pat. Nos. 4,823,684 and 5,251,607, both to Joseph Traeger, et al. Over the years there have been many improvements and variations of these products made but their essential principal of operation remains the same. An electrically driven auger transports small compressed wood pellets from an exterior hopper to a typically open top cylindrical combustion chamber, or firepot, inside an enclosed cooking chamber with an openable lid. This combustion chamber is supplied with combustion air pressurized and driven by an exterior fan through ductwork to an area surrounding the firepot and then though holes in the exterior of the firepot feeding air into the combustion space. The hot gas from the firepot is conveyed through a series of baffles to a cooking grate placed above the firepot and baffles where it heats the food placed on the cooking grate.

Such appliances may be used to cook meat, often in large pieces, such as roasts or briskets. Cooking may take place for long periods of time (on the order of hours), at low to moderate temperatures of 200° F. to 400° F. Sizes of appliances and cooking surfaces may vary as there is a desire to accommodate large quantities of meat. To provide even cooking across the cooking grate area, the set of baffles above the firepot must be optimized to produce a relatively low thermal intensity in terms of energy output per unit of area. However, the temperatures attained at the cooking grate are linearly proportional to the thermal intensity. Temperatures of 600° F. to 800° F. needed to provide searing while grilling smaller pieces of meat such as steaks or hamburgers for a shorter period of time (on the order of minutes) requires a much higher energy output per area.

Using appliances having a relatively large cooking area (common in the marketplace) it may become very difficult to obtain these higher thermal intensities simply by upsizing, or by more rapidly running the auger feed from the pellet hopper. Such difficulty is, first of all, based on the problem of evenly distributing heat from a concentrated heat source (e.g., a single firepot), to a large, typically rectangular, cooking area without absorbing or losing too much heat in the baffle structure necessary to accomplish this. A second difficulty, from a commercial point of view, is the expense of scaling up the auger drive and combustion air fan delivery and firepot structure. Thus, it has remained the case that most such pellet appliances described do not perform well for grilling, particularly in providing high cooking grate temperatures to create searing action on the exterior.

What is needed is a system and device for addressing the above, and related, problems.

SUMMARY OF THE INVENTION

The invention of the present disclosure, in one aspect thereof, comprises a cooking grill having a firepot configured to burn pelletized fuel fed from an auger. The cooking grill has a cooking grate above the firepot. A double walled enclosure interposes the firepot and the cooking grate and contains and directs flow of combustion gases from the firepot up to the cooking grate.

In some embodiments, the firepot has an exhaust opening from which combustion gases flow. An area defined by the exhaust opening may be smaller than an area defined by the cooking grate.

In some cases, the double walled enclosure encloses a volume between the firepot and cooking grate through which the exhaust gases flow and prevents the combustion gases from escaping the cooking grill unless first flowing through the cooking grate. The double walled enclosure may also further comprise an inner wall spaced apart from an outer wall. The inner and outer wall may define an airspace therebetween. In some embodiments, a space between the inner and outer walls is filled with a solid or other type of insulation material.

Some embodiments of the cooking grill include a pyramidal baffle inside the double walled enclosure for arresting sparks and embers flowing upward from the firepot. The baffle may be affixed to an interior wall of the double walled enclosure. The interior wall of the double walled enclosure may define a rectilinear cross section in a horizontal plane therethrough. The baffle may extend from the interior wall toward a center of the volume enclosed by the double walled enclosure.

Some embodiments of the cooking grill further comprising a drip tray at a bottom of the double wall enclosure surrounding the firepot. A lip may be situated proximate the firepot to prevents drippings on the drip tray from running into the firepot.

The invention of the present disclosure, in another aspect thereof, comprises a cooking grill having a firebox containing a pellet burning firepot that is fed pelletized solid fuel from an auger and fed combustion air under positive pressure from outside the cooking grill. The cooking grill has a food grate heated by combustion gases from the firepot and selectively coverable by a lid hingedly attached to the firebox. The grill includes a double walled structure accepting the combustion gases at a first lower end and preventing escape of the combustion gases until the combustion gases reach the food grate. The double walled structure has a horizontal cross section at a lower portion that defines a smaller area than a horizontal cross section at an upper portion.

In some embodiments of the instant cooking grill, the double walled structure comprises an inner wall spaced from an outer wall with air between the inner wall and outer wall. In some cases, insulating material is placed between the inner wall and outer wall.

The cooking grill may contain a baffle inside the double walled structure. A drip tray may also be provided under the double walled structure and surrounding a top portion of the firepot. There may be a lip on the drip tray preventing drippings from running into the firepot.

The invention of the present disclosure, in another aspect thereof, comprises a cooking grill having a firebox supporting a food grate and containing a firepot fueled by solid pellet fuel and receiving combustion air under positive pressure. The grill has a double walled structure inside the firebox interposing the firepot and the food grate, the double walled structure defining a manifold directing combustion gases from the firepot to the fuel grate. The cooking grill has a peaked baffle inside the double walled structure manifold placed to arrest movement of sparks and solid matter rising from the firepot, and a drip tray surrounding the firepot and having a lip placed to prevent drippings from the drip tray from moving into the firepot.

In some embodiments, a combustion outlet opening of the firepot is of a smaller area than an area defined by the cooking grate and the double walled structure is shaped to allow the combustion gases to expand to pass through substantially all of the food grate without substantial loss of combustion gases prior to reaching the food grate. In some cases, the double walled structure is insulated to reduce heat loss.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now toFIG.1, a perspective view of a cooking grill according to aspects of the present disclosure is shown. From the exterior, the grill100can be seen to comprise a firebox102with an openable lid104. The lid104may be hinged from the back and have a handle for opening and closing. A front pellet feeding hopper system106can be seen where the user feeds fuel pellets for auguring into the firebox for combustion. The pellet feeding hopper system106or another such system may also be mounted to the back, left side or right side of the grill100. Side shelves108and other helpful implements may be provided in various embodiments.

FIG.2is a front perspective cutaway view of the cooking grill ofFIG.1.FIG.3provides a complementary side perspective cutaway view. Here the interior of the firebox102can be seen, including a cooking grate202placed above a heat or combustion source. In the present embodiment, the heat source includes a firepot204. The firepot204may have perforations or air openings for receiving combustion air from an air duct206. In some embodiments, air in the duct206is pressurized to drive air into the firepot204to control or enhance the combustion of wood pellets or other fuel in the firepot204. Fuel may be driven into the firepot204by an auger or other motive device and may be controlled by a user, thereby providing additional control over the heat and combustion within the firebox102. Heated combustion gases may flow from the firepot204via exhaust or combustion opening219. In some embodiments the opening219is round corresponding with an overall cylindrical shape of the firepot204.

A double walled enclosure208provides for transport of heated gases and combustion products from the firepot204to the cooking grate202. It will be appreciated that an area defined by the opening219may be much smaller in area that the cooking grate202. As the firepot204may be a relatively small and/or concentrated heat and combustion source relative to the surface area of the cooking grate202, the double walled enclosure208provides for transport of the combustion products and heat from the firepot204to the cooking grate202in such a manner as to heat most or all of the cooking grate202to a high temperature suitable for grilling.

The double walled enclosure may be thought of as a manifold for transport of the heated gas and combustion products to the cooking grate202. With the decrease in thermal loss into the firebox102and out of the same from the concentrated heat source of the firepot204the firepot204provides sufficient heat not only for low temperature slow cooking, but also and for higher temperature grilling and searing operations at the cooking grate202.

The double walled enclosure208may provide an outer wall210with an inner wall212nested therein but spaced apart therefrom. An insulating air space211may thereby be defined between the inner wall210and outer wall212. In some embodiments, the space211is not empty or air-filled but filled with an insulating material. The insulating material may comprise ceramic mineral wool type insulation, a high temperature aerogel, or some other form of additional heat barrier interposed between the inner wall210and the outer wall212. In some embodiments, only a portion of the space211may be insulated (for example, nearest to the cooking grate202or nearest to the firepot204).

In some embodiments, the enclosure208is double walled across all of the vertical distance between the firepot204and the cooking grate202. In other embodiments, the enclosure spans the entire vertical space, but is double walled across only a portion of the vertical distance (e.g., nearest the cooking grate202, for example). It may also be double walled only on a lower portion, or only on a medial portion. In some embodiments, the inner wall212may be equidistantly spaced from the outer wall210. In other embodiments the walls210,212may be spaced closer together near the cooking grate202or lower near the firepot204.

In some embodiments, a drip pan216sits below the double walled enclosure208and joins to the firepot204. The drip pan216may collect any grease or other drippings from the cooking grate202that may run down the inner wall212toward the firepot204. In some embodiments, a lip218surrounds the top opening of the firepot204to prevent collected grease from running into the firepot204and affecting heat or burn characteristics. The drip pan216may be removable, or provide drainage holes into a catch cup or the like for emptying grease and other accumulations.

As discussed above, certain ash and coal particles may escape from the firepot204during combustion. These may tend to travel upwardly with the convection currents of the heated gases. A baffle214may be provided within the enclosure208to help arrest such particles. The baffle214may be a single or multi-piece component. In some embodiments, it is located within and affixed to the inner wall212of the enclosure208. The enclosure208may be generally square or rectangular in horizontal cross section to conform to the square or rectangular shape that may be seen in the cooking grate202, and to guide gases from the firepot204accordingly. The baffle214may be configured to extend horizontally from the relatively flat sides of the inner wall212, and/or from the “corners” of the inner wall212as a horizontal rectilinear cross section is defined by the inner wall212.

FIG.4is a top down view into the firebox of the cooking grill ofFIG.1with the baffle214ghosted to show components placement. Viewed from above, the baffle214has a rectilinear outline. The baffle214may be centered over the firepot204, which may be centered in the drip tray216. However, these components are not necessarily centered in all embodiments. In some embodiments, the inner wall212may comprise four downward sloped planar panels402,404,406,408, which may correspond to right, left, front, and back sides, respectively (if viewed, for example, from the front of the cooking grill100). It should be understood that the outer wall210may be comprised of corresponding panels.

It should also be understood that the illustrated embodiments of the present disclosure describe an enclosure208having a rectilinear cross section. This configuration accommodates a rectangular cooking grate202and is at least partially responsible for the ability of systems of the present disclosure to evenly heat a large cooking grate having a shape different from that of the firepot204(e.g., round). However, in embodiments where a round cooking grate is provided, the enclosure208and baffle214may have a corresponding round horizontal cross section. In other embodiments, it may be that only a portion of the cooking grate202would be heated by the firepot204such that the horizontal cross section of the enclosure208may not directly correspond directly to the shape or dimensions of the cooking grate202.

Standoffs302may be provided that affix the baffle214to one or more of the panels402,404,406,408of the inner wall212. Thus gaps304may be provided interposing the baffle214and one or more of the panels402,404,406,408. The gaps304allow for flow of combustion gases but the baffle214itself impedes flow of cinders and other solid particles. The gaps304also allow for liquids and other materials that might fall through the cooking grate202to be directed to the drip tray216but away from the firepot204. The gaps304may not be uniform between the baffle214and one or more of the panels402,404,406,408. Further, spacing between the baffle214and one or more of the panels402,404,406,408may vary within a particular gap304. In some embodiments, gaps304are only present between one, two, or three of the402,404,406,408and the baffle214(in other words the baffle214may attach to one or more of the panels402,404,406,408such that there is no gap at such panel).

FIG.5is a top down view into the firebox102of the cooking grill100ofFIG.1. As can be seen from this viewpoint in conjunction with the perspective views ofFIGS.2-3, the baffle214may have a pyramidal shape with four walls502,504,506,508rising upward toward the cooking grate202from near the respective panels402,404,406,408of the inner wall212of the enclosure208. In some embodiments, each panel402,404,406,408is spaced apart from each wall502,504,506,508with a standoff302, spacing fastener, or the like such that there is a gap304between each respective panel/wall pair. This may promote even heating of the cooking grate202. However, in other embodiments, gaps304may not be provided between each panel/wall pair. Additionally, the baffle214may not attach to each of the four panels402,404,406,408although in some embodiments this promotes stability of the baffle214.

The four walls502,504,506,508may meet at an apex510corresponding to the upper most point of the baffle214. The baffle214, in addition to trapping cinders, ash, and other solid particles and preventing them from reaching the cooking grate202, may also serve as a thermal re-emitter. As the baffle214is heated from combustion gases, it may radiate a significant amount of heat toward the cooking grate202. Furthermore, the baffle214may serve as a vaporizer plate that converts fat or other drippings to smoke to enhance flavor of food being cooked on the cooking grate202. Finally, the sloped walls502,504,506,508guide anything falling onto the baffle214that is not vaporized onto the respective panels402,404,406,408of the inner wall212where they may fall onto the drip tray216.

It should be appreciated that the baffle214may be the only baffle between the firepot204and the cooking grate202. In some embodiments, the baffle214is imperforate and does not admit any combustion products therethrough (in other words, all gas air or fluid flow from the firepot to the cooking grate202is via the one or more gaps304). In other embodiments the baffle214could have openings or apertures (not shown) to redistribute convective heat from the combustion gases produced in the firepot204. Such openings may take the form of piercings, holes of various shapes, grids, screens, hooded openings, louvres, or other openings. In other embodiments, openings through the baffle214may take the form of a pipe, tunnel, or tortured path such that some convection gases may flow through but solid materials such as cinders and ash are not likely to flow through.

The term “at least” followed by a number is used herein to denote the start of a range beginning with that number (which may be a ranger having an upper limit or no upper limit, depending on the variable being defined). For example, “at least 1” means 1 or more than 1. The term “at most” followed by a number is used herein to denote the end of a range ending with that number (which may be a range having 1 or 0 as its lower limit, or a range having no lower limit, depending upon the variable being defined). For example, “at most 4” means 4 or less than 4, and “at most 40%” means 40% or less than 40%.