Firebox for pellet grills

Abstract

A combustion chamber has an inner wall defining an inner chamber. The inner wall is perforated to allow combustion air to enter the inner chamber. The combustion chamber has an outer wall defining an outer chamber. The outer wall is perforated to allow combustion air to pass from a pressurized air plenum to the inner wall. The inner wall and the outer wall are spaced apart so that air can flow between the inner wall and the outer wall.

Description

[0001] Cross-references to related cases

[0002] This application claims the benefit of U.S. Provisional Patent Application Serial No. 62 / 811,743, filed on February 28, 2019, and is incorporated by reference into the present disclosure as if fully set forth herein. Technical Field

[0003] The present disclosure relates particularly to pellet fuel grills, and more particularly to a combustion chamber used in a pellet fuel grill. Background Art

[0004] Early examples of outdoor wood pellet-fired cooking and smoking appliances are disclosed in U.S. Pat. Nos. 4,823,684 and 5,251,607 to Traeger et al. Over the years, there have been some improvements and variations of these products that have been manufactured, but their basic operating principles remain the same. With regard to the handling and combustion of wood fuel pellets, problems can arise internally. Combustion air must reach the fuel pellets, but existing furnace designs can lead to blockage of the air intake holes. The air intake holes may be blocked due to the arrangement of particles in the furnace, ash or debris blocking the holes, or for other reasons. This can result in unacceptably low heat output and can even cause the furnace to completely extinguish. In addition, in smoldering or other operating modes, unburned hydrocarbons may escape the furnace in gaseous form and be ignited unnecessarily elsewhere. Further, uneven air flow into the furnace can lead to hot spots or cold spots and unburned fuel areas. On the other hand, fuel may be consumed in unexpected places, such as in a fuel supply mechanism or other delivery device.

[0005] What is needed is a system and method for solving the above-referenced and related problems. Summary of the invention

[0006] The disclosed invention includes, in one aspect thereof, a combustion chamber having an inner wall defining an inner chamber. The inner wall is perforated to allow combustion air to enter the inner chamber. The combustion chamber has an outer wall defining an outer chamber. The outer wall is perforated to allow combustion air to pass from a pressurized air plenum to the inner wall. The inner wall and the outer wall are spaced apart so that air can flow between the inner wall and the outer wall. The inner chamber has an open top to receive a solid fuel for combustion in the inner chamber.

[0007] In some embodiments, the combustion chamber includes a funnel portion above the inner chamber, the funnel portion being configured to guide the solid fuel into the inner chamber. The inner chamber and the outer chamber may be bounded by a common floor. The outer wall may have perforations at least above the inner wall and at the same vertical height as the inner wall. The outer wall may also have perforations vertically above the funnel portion.

[0008] In some embodiments, the combustion chamber further comprises a perforated floor in the inner chamber. Such a floor may have an inclined section of the perforated floor on the side of the inner chamber opposite to the location where the solid fuel is introduced. The ash chamber may be below the perforated floor. In some cases, the lower outer chamber extension is defined by the lower outer wall extension and contains the ash chamber in the lower outer chamber extension. Some embodiments include a spaced apart area between the ash chamber and the lower outer chamber extension, the spaced apart area having a lip extending inwardly to collect debris in the spaced apart area. A removable cap may be placed at the bottom end of the ash chamber.

[0009] The invention disclosed herein includes, in another aspect thereof, a cooking grill having a cooking chamber having a cooking grate supported therein, the cooking grate being accessible through an openable cover. The grill may have a hearth within the cooking chamber, below the cooking grate, an air plenum that provides pressurized combustion air to the hearth, and a fan that pressurizes the air in the plenum. The hearth also includes an inner wall and an outer chamber wall, the inner wall defining an inner chamber where fuel is burned, and an outer chamber wall defining an outer chamber containing the inner chamber. The outer chamber wall is fixed within the plenum and receives pressurized air from the plenum. The inner wall and the outer wall are spaced apart so that air can flow freely within the outer chamber and around the inner chamber. The inner chamber is perforated to receive combustion air from the outer chamber.

[0010] The grill may have a perforated floor below the inner chamber, and may have an ash compartment below the perforated floor. A fuel supply may traverse the plenum and through the outer chamber wall to deliver fuel into the top of the inner chamber. A funnel may be provided on the inner chamber wall to direct solid fuel from the fuel supply into the inner chamber. The perforated floor may include an inclined section and a flat section, the inclined section oriented to direct fuel particles from the fuel supply toward the flat section.

[0011] The disclosed invention includes, in another aspect thereof, a cooking grill having a cooking chamber and a hearth, the cooking chamber including a cooking grate, the hearth being below the cooking grate and at least partially within an air plenum that provides pressurized air to the hearth. The hearth has an outer chamber defined by a perforated outer chamber wall that is in fluid contact with the pressurized air in the plenum. The hearth has an inner chamber within the outer chamber and defined by a perforated inner chamber wall, the perforations of the inner chamber wall being sized to prevent unburned fuel particles from passing through the perforations of the inner chamber wall, but to permit air flow from the outer chamber through the perforations of the inner chamber wall.

[0012] The grill may include a perforated floor below the inner chamber that allows embers to fall from the inner chamber to an ember chamber at least partially below the plenum. The grill may also include a fuel supply mechanism that passes through a portion of the plenum and through the outer chamber wall and is positioned to provide fuel into the top of the inner chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A perspective cutaway view of a pellet grill.

[0014] Figure 2 is a side cross-sectional view of a combustion chamber for a pellet grill or other device according to aspects of the present disclosure.

[0015] Figure 3 for Figure 2 Perspective cutaway transparent interior view of a combustion chamber.

[0016] Figure 4 is a side cross-sectional view of another embodiment of a combustion chamber for a pellet grill or other device according to aspects of the present disclosure.

[0017] Figure 5 for Figure 4 Perspective cutaway transparent interior view of a combustion chamber.

[0018] Figure 6 is a perspective cross-sectional view of another embodiment of a combustion chamber according to aspects of the present disclosure. DETAILED DESCRIPTION

[0019] Reference now Figure 1 , showing a perspective cutaway view of a pellet grill 100. The pellet grill 100 may be of the type that utilizes pelletized fuel, which includes wood, sawdust, or other ingredients formed into a pelletized form for processing and combustion by the grill 100 for cooking or smoking operations. The pellet-burning cooking grill 100 provides a firebox or cooking chamber 102 that contains or supports a cooking grate 103. An openable or hinged cover 104 may be provided for selective access to the cooking grate 103. A fuel supply mechanism 110 (here shown as an auger, but may also be, for example and without limitation, a belt conveyor, a rod / slide conveyor, a push feeder, or other fuel supply mechanism) may transport compressed wood pellets or other pelletized fuel from an external hopper 108 to a typically open-top cylindrical hearth or combustion chamber 120. The combustion chamber 120 may be supplied with combustion air that is pressurized and driven by a fan, through a duct system or plenum 114 to an area surrounding the furnace 120, and then through holes in the exterior of the furnace, thereby supplying air into the interior combustion space. In some configurations, the auger 110 operates in an auger duct 112 that is at least partially located within the plenum 114.

[0020] The resistance igniter 116 may initiate combustion of the fuel inside the combustion chamber 120. The hot gases from the combustion chamber 120 may be delivered through a series of baffles 118 to the cooking grate 103 placed above the combustion chamber 120.

[0021] Reference now Figure 2 , shows a side cross-sectional view of a combustion chamber 200 for a pellet grill 100 or other device according to aspects of the present disclosure. In various embodiments, the combustion chamber 200 is a replacement for the combustion chamber 120. In some embodiments, because the combustion chamber 200 is a "drop-in" replacement (although it is understood that the combustion chamber 200 may still be inserted, assembled, secured in place, etc. during the original production of the grill 100 or its associated subcomponents), the grill 100 is not further modified. However, the plenum 114, cooking grate 103, cooking chamber 102, etc. may be sized to take full advantage of the combustion chamber 200. To further illustrate, Figure 3 for Figure 2 A perspective cutaway transparent interior view of the combustion chamber 200 .

[0022] Combustion chamber 200 includes inner chamber 202, which is limited by inner wall 205 or container for burning fuel particles. Inner wall 205 can be perforated (as shown), or can include other perforated configurations. Perforations 203 can have a variety of sizes and shapes so that they completely retain fuel particles while allowing pressurized combustion airflow to freely pass to the burning particles inside inner chamber 202. In some cases perforations 203 can be very small, so as to define a screen. Inner chamber wall 205 can include heat-resistant materials (such as metal alloys) so that it can withstand long-term high temperatures from burning fuel particles.

[0023] In terms of shape, the inner chamber 202 may be cylindrical, toroidal, or prismatic, as this is most advantageous for matching with the outer chamber 206 (which may be defined by the outer wall 209 or container). The inner chamber 202 and the outer chamber 106 may be cylindrical and / or coaxial with respect to each other. A space 207 may be defined between the inner chamber 202 and the outer chamber 206. The space 207 may be generally toroidal, so that the distance between the inner chamber 202 and the outer chamber 206 is substantially the same anywhere between them.

[0024] The outer chamber wall 209 may define openings or holes 208 that receive air driven or pressurized by the fan 115 from the plenum 114. The holes 208 defined by the outer chamber 206 may vary in size and spacing. In one embodiment, the holes 208 are defined vertically above the inner chamber 202. In some embodiments, another set of holes 214 are defined through the outer chamber wall 209 so as to vertically overlap the inner chamber 202 completely or partially. Another series of holes 210 may be provided near the igniter 116 to ensure proper ignition operation. Like the holes 208, the holes 214 and 210 may be supplied with pressurized air driven by the fan 115 from the plenum 114.

[0025] The outer chamber 206 may be cylindrical in form, although other configurations are possible. The dimensions of the inner chamber 202 (in volume or in diameter) may match the dimensions of a single hearth seen in the prior art. The inner chamber 202 may be sized to provide the thermal performance required of the grill 100 into which it is mounted. In some embodiments, the outer chamber wall 209 is sized to be at least larger than prior art hearths, which helps provide the benefits outlined herein and others.

[0026] In some embodiments, the inner chamber 202 shares a common floor 212 with the outer chamber 206. In some embodiments, the outer chamber 206 provides the floor 212, and the inner chamber 202 includes a wall on the floor 212 located inside the outer chamber 206. An ash opening (which can also be closed, not shown) can be provided into the combustion chamber 200 via the floor 212. The inner chamber 202 and the outer chamber 206 can have an open top. In some embodiments, the inner chamber 202 is shorter than the outer chamber 206 so as to fit completely inside the outer chamber 206.

[0027] The auger 110 and / or auger duct 112 may enter the combustion chamber 200 via an opening through the outer chamber 206 and to an area above the inner chamber 202 so that particles fall from the auger duct 112 into the inner chamber 202. The inner chamber 202 may have a funnel 204 on or near the top thereof to help prevent particles from bouncing or falling out of the inner chamber 202.

[0028] Reference now Figure 4 , shows a side cross-sectional view of another embodiment of a combustion chamber 400 for a pellet grill 100 or other device according to aspects of the present disclosure. Figure 5 4 is a perspective cutaway transparent interior view of the combustion chamber 400. There are some commonalities between the combustion chamber 400 and the combustion chamber 200 discussed above, and components are understood to be common unless otherwise stated. Both combustion chambers 200, 400 (as well as the combustion chamber 600 described below) are designed to solve various problems associated with prior art fireboxes and are upgrades, replacements, or OEM parts for solid fuel (e.g., pellet) grills.

[0029] The combustion chamber 400 provides an extension 408 chamber of the outer chamber 206 that may extend below the floor 402 and / or even the plenum chamber 114. The extension chamber 408 may be defined by an outer wall extension 409 that may be integral with the outer wall 209 or separately fixed relative to the outer wall 209. The inner chamber 202 may also be taller or longer such that it extends all the way to or near the floor 416 of the outer chamber extension 408 while maintaining its upper position relative to the outer chamber 206 and the auger conduit 112.

[0030] The inner chamber 202 may be divided into two parts by a perforated floor 402. The floor 402 may provide a surface for burning fuel particles while allowing ash to fall into an ash chamber 410 below the floor 402. In this embodiment, the ash chamber 410 may be defined by a portion of the inner chamber wall below the floor 402. The floor 402 may be perforated or have an open portion or a screen portion to allow ash and other byproducts to fall through. The floor 402 may support unburned or burning solid fuel while allowing ash to fall away so that it does not hinder further continued combustion.

[0031] The bottom plate 402 may provide an inclined section 404 opposite a side where the auger conduit 112 is located above the bottom plate 402. This may promote uniform distribution of the fuel particles as they fall from the auger conduit 112. The inclined section 404 may be provided at an angle of approximately 45 degrees. In other embodiments, the angle may vary (e.g., within a range from approximately 30 degrees to approximately 60 degrees). As may be seen in FIG. Figure 4 As seen in the side cross-sectional view of FIG. 4 , the inclined segment 404 may occupy less than half of the diameter of the interior 203, while the remainder of the bottom plate 402 remains substantially flat. In some embodiments, the inclined segment 404 comprises approximately 10-20% of the diameter of the interior chamber 202. In one embodiment, the inclined segment 404 comprises approximately 17.6% of the diameter of the interior chamber 202 (as shown in all figures when viewing the interior profile).

[0032] Between the inner chamber 202 and the outer chamber extension 408 (and possibly below the floor 402) is a collector 414. The lip 412 allows ash and debris particles to fall into the collector 414 and away from the sides of the inner chamber 202 near the upper portion (where combustion occurs). Ash, debris particles, and / or other debris are thereby prevented from accumulating around the inner chamber 202 where unimpeded airflow into the inner chamber 202 is desirable to promote proper combustion of the fuel particles. The collector 414 and the ash collector 410 may be accessible through one or more closable openings (not shown) in the floor 416 or elsewhere.

[0033] Reference now Figure 6, shows a perspective cutaway view of another embodiment of a combustion chamber 600 according to aspects of the present disclosure. The combustion chamber 600 shares common components with the combustion chambers 200, 400 unless otherwise indicated. The combustion chamber 600 may include an inner chamber 202 defined by an inner wall 205 positioned within an outer chamber 206 defined by an outer wall 209. The inner chamber 202 may be coaxial with the outer chamber 206. The outer chamber wall 209 may fit into the plenum 114 to receive positive combustion air via one or more series of openings 208, 210, 214 to the plenum 114.

[0034] The inner wall 205 may be perforated or screened to allow air flow into the inner chamber 202 where the fuel particles are burned after being introduced via the auger conduit 112. Also in this embodiment, the bottom plate 402 is perforated to allow ash and debris to fall through. An inclined section 404 of the bottom plate 402 is also provided. In this embodiment, the inner wall 205 does not extend below the bottom plate 402, but rather the outer chamber extension 408 is an undivided compartment or ash chamber 410. Extending from the lower portion of the outer wall extension 209 is a bracket 606 that supports a locking nut 604 or other fastener receiving device. Here, a removable bottom cap or cover 602 can be held against the outer wall extension 409 by a bolt 608 entering the nut 604. In some embodiments, the bolt 608 is locked to the bottom cover 608 so that the cover 608 can be screwed into the outer wall extension 409.

[0035] A support member 610 is disposed between the inner wall 205 and the outer wall 209 to support the inner wall 205 in a suitable position relative to the outer wall 209 and / or the extension 409. This may replace the lip 412 or be in addition to the lip 412 ( Figure 4-5 ). In the case where the inner chamber 202 and the outer chamber 206 are cylindrical and coaxial, the support member 610 may be annular. The support member 610 may be perforated to allow any spilled fuel particles, ash or other debris that falls between the locations of the inner wall 205 and the outer wall 209 to pass into the ash chamber 410 (here defined by the outer wall extension 409). In other embodiments, the funnel portion 204 of the inner chamber wall 205 may extend so as to be close enough to or in contact with the outer wall 209 so that the support area 610 does not need to be perforated.

[0036] * * * *

[0037] It should be understood that the terms "comprises", "includes", "contains" and their grammatical variations do not exclude the addition of one or more components, features, steps or integers or combinations thereof, and the terms should be interpreted as specifying components, features, steps or integers.

[0038] If the specification or claims refer to "an additional" element, that does not preclude there being more than one of the additional element.

[0039] It should be understood that where the claims or specification refer to "a" or "an" element, such reference is not to be construed as meaning that there is only one of the element.

[0040] It should be understood that where the specification states a component, feature, structure, or characteristic “may,” “might,” “could,” or “could” be included, that particular component, feature, structure, or characteristic is not required to be included.

[0041] Where applicable, although state diagrams, flow charts, or both may be used to describe embodiments, the present invention is not limited to these diagrams or corresponding descriptions. For example, a flow need not move through each of the boxes or states shown, or in exactly the same order as shown and described.

[0042] The methods of the present invention may be implemented by performing or completing selected steps or tasks manually, automatically, or a combination thereof.

[0043] The term "method" may refer to ways, means, techniques and procedures for completing a given task, including but not limited to those ways, means, techniques and procedures known to practitioners in the field to which the invention belongs, or those ways, means, techniques and procedures that can be easily developed by practitioners in the field to which the invention belongs from known ways, means, techniques and procedures.

[0044] The term "at least" followed by a number is used herein to indicate the beginning of a range that begins with that number (which may be a range with an upper limit or without an 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 indicate the end of a range that ends with that number (which may be a range with 1 or 0 as its lower limit, or a range with no lower limit, depending on 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%.

[0045] In this document, when a range is given as "(first number) to (second number)" or "(first number) - (second number)", this means a range with the first number as the lower limit and the second number as the upper limit. For example, 25 to 100 should be interpreted as meaning a range with a lower limit of 25 and an upper limit of 100. In addition, it should be noted that where a range is given, every possible subrange or interval within the range is also specifically intended unless the context indicates otherwise. For example, if the specification indicates a range of 25 to 100, such a range is also intended to include subranges such as 26-100, 27-100, etc., 25-99, 25-98, etc., and any other possible combination of lower and upper values ​​within the stated range, such as 33-47, 60-97, 41-45, 28-96, etc. Note that integer range values ​​have been used in this paragraph for illustration purposes only, and decimal and fractional values ​​(eg, 46.7-91.3) should also be understood to be intended as possible sub-range endpoints unless specifically excluded.

[0046] It should be noted that where a method comprising two or more defined steps is referred to herein, the defined steps can be performed in any order or simultaneously (unless the context excludes this possibility), and the method may also include one or more other steps performed before any defined step, between two defined steps, or after all defined steps (unless the context excludes this possibility).

[0047] Further, it should be noted that approximate terms (e.g., "approximately," "roughly," "approximately," etc.) should be interpreted according to the ordinary and customary meanings used in the relevant art, unless otherwise indicated herein. In the absence of a specific definition within the present disclosure and in the absence of ordinary and customary usage in the relevant art, such terms should be interpreted as plus or minus 10% of the base value.

[0048] Unless otherwise indicated, the term "selective" or "selectively" is used to mean that an operation or function can be performed by the referenced structure or device, but the operation or function may not occur continuously or without interruption. In addition, a selective operation or a selectively performed operation may be an operation that a user or operator of a device or method can choose whether or when to perform, but the function or operation can still be fully operational on or in the relevant device, machine or method.

[0049] * * * * *

[0050] The present invention is therefore well adapted to carry out the objects and attain the ends and advantages mentioned above as well as those inherent therein. While the inventive apparatus has been described and illustrated by reference to certain preferred embodiments with respect to the accompanying drawings associated therewith, various changes and further modifications besides those shown and illustrated herein may be made therein by one of ordinary skill in the art without departing from the spirit of the inventive concept as defined by the appended claims.

Claims

1. A combustion chamber (200, 400, 600), comprising: an inner wall (205) defining an inner chamber (202), the inner wall being perforated to allow combustion air to enter the inner chamber; an outer wall (209) defining an outer chamber (206) and extending upwardly beyond the inner wall to a top of the pressurized air plenum, the outer chamber being contained within and surrounded by the pressurized air plenum, the outer wall being perforated with a plurality of openings (208, 210, 214) to allow combustion air to pass from the pressurized air plenum surrounding the outer wall to the inner wall; wherein the inner wall and the outer wall are equally spaced apart so that air can flow between the inner wall and the outer wall; and wherein the inner chamber has an open top to receive solid fuel for combustion in the inner chamber, wherein the perforations of the inner wall (205) are sized to prevent unburned fuel particles from passing through the perforations of the inner wall but to allow air flow from the outer chamber (206) through the perforations of the inner wall, wherein the inner chamber (202) shares a common floor (212) with the outer chamber (206), the perforated floor (212) below the inner chamber (202) allowing ash to fall from the inner chamber (202) to an ash chamber at least partially below the booster chamber.

2. The combustion chamber according to claim 1, characterized in that The combustion chamber also includes a funnel portion (204) above the inner chamber, the funnel portion being configured to guide solid fuel into the inner chamber.

3. The combustion chamber according to claim 2, characterized in that The outer wall has perforations at least above and at the same vertical height as the inner wall.

4. The combustion chamber according to claim 3, characterized in that The outer wall has a perforation vertically above the funnel.

5. The combustion chamber according to claim 1, characterized in that The combustion chamber also includes an inclined section (404) of the perforated floor on a side of the interior chamber opposite to where the solid fuel is introduced.

6. The combustion chamber according to claim 1, characterized in that The combustion chamber further comprises a lower outer chamber extension (408) defined by a lower outer wall extension (409) and containing the ash chamber therein.

7. The combustion chamber according to claim 6, characterized in that The combustion chamber also includes a spaced apart area between the ash chamber and the lower outer chamber extension, the spaced apart area having an inwardly extending lip (412) to collect debris in the spaced apart area.

8. The combustion chamber according to claim 1, characterized in that The combustion chamber further comprises a removable cap (602) at a bottom end of the ash chamber facing the floor of the inner chamber.

9. The combustion chamber according to claim 1, characterized in that The inner chamber matches the shape of the outer chamber.

10. The combustion chamber according to claim 9, characterized in that The inner chamber and the outer chamber are cylindrical.

11. A cooking grill (100), comprising: a cooking chamber (102) having a cooking grate (103) supported therein, the cooking grate being accessible through an openable cover (104); a hearth (120) within the cooking chamber and below the cooking grate; an air plenum (114) that provides pressurized combustion air to the furnace; and a fan (115) that pressurizes air in the plenum; The furnace further comprises a combustion chamber according to any one of claims 1 to 10, The outer chamber wall is fixed within the plenum chamber and receives pressurized air from the plenum chamber.

12. The cooking grill of claim 11, wherein: The cooking grill also includes a fuel supply mechanism (110) that traverses the plenum chamber and passes through the outer chamber wall to deliver fuel into the top of the inner chamber.

13. The cooking grill of claim 12, wherein: The cooking grill also includes a funnel on the inner chamber wall that directs solid fuel from the fuel supply into the inner chamber.

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