Variable Fuel Cooker

This application is a continuation of U.S. patent application Ser. No. 18/946,801 filed Nov. 13, 2024; which claims the benefit of priority from U.S. Provisional Patent Application No. 63/640,706 filed Apr. 30, 2024, the contents of which are incorporated herein by reference.

The present invention relates to systems and devices for delivering combustible material to a burn box for use in cooking appliances such as grills, smokers, or other types of cookers.

Grills and smokers have long been popular tools for outdoor cooking, with wood pellets often used as fuel due to their ability to provide consistent heat and flavor. However, wood pellets are expensive to produce, requiring a significant amount of energy. The process involves grinding wood into fine sawdust, pushing it through a die under high temperature and pressure to melt the lignin, and then rapidly cooling the material to form pellets. This energy-intensive process may reduce the wood's natural flavor imparted by guaiacol-a key molecule responsible for the distinct taste of smoked foods.

Wood chips, by contrast, require only minimal processing-typically just one or two passes through a chipper-without the need for high energy consumption or complex machinery. As a result, wood chips offer a good alternative to pellets. Furthermore, it is believed that wood chips, due to the preservation of guaiacol during the chipping process, may impart a richer, more authentic wood smoke flavor to food compared to pellets.

In addition to requiring minimal processing, wood chips offer functional advantages in grilling, such as retaining higher moisture content than pellets. Wood chips used in the grills typically contain 15-20% moisture, compared to the 8-10% moisture found in wood pellets. This higher moisture content enhances the grilling process, helping to keep food moister and more tender by releasing steam as the wood burns. The result is juicier, more flavorful grilled meats, such as rotisserie chicken, that benefit from the increased moisture released during cooking.

Despite the advantages of wood chips, their use in grills and smokers has been limited due to challenges in reliably delivering them to the firebox. Wood chips, being irregular in shape and size, are prone to jamming, which can interrupt the flow of fuel and cause inconsistent cooking temperatures. The present invention addresses these issues by providing a reliable system for delivering wood chips or other irregular combustible material to a firebox, particularly in a barbecue grill setting, as well as to reduce backflow of combustion gases.

Moreover, due to different structural and functional demands related to burning the different types of fuel, it has not been possible or practical to provide for grills or smokers configured to effectively use both wood pellets and wood chips. The present invention addresses these issues and provides increased versatility by allowing users to switch between wood pellets and wood chips, depending on fuel preference or availability. Unlike traditional pellet grills that are limited to pellet fuel, this dual fuel capability ensures greater convenience and flexibility. Users can choose pellets when a milder smoke flavor or choose wood chips when seeking a more robust smoke flavor, or otherwise dependent on fuel availability. This adaptability provides significant practical benefits, especially in situations when specific cooking outcomes are desired, such as baking, or where one fuel type may be unavailable.

The present invention is directed to an auger-based material transport system designed to prevent jamming, ensure consistent material flow, and reduce backflow of combustion gases, while enabling the use of irregularly shaped and sized combustible materials. The invention also addresses mechanisms for controlling the flow of combustible material, reducing the risk of bridging, and enhancing overall system reliability and efficiency. The invention also incorporates an automated switching and programming system that adjusts operational parameters such as auger speed, fan speed, and hopper agitation based on the type of combustible material being used, further optimizing fuel delivery, combustion efficiency, and temperature control.

The invention features an auger tube larger in diameter than the auger itself, allowing the auger to pivot when it encounters larger chips, thus preventing jams. This design has proven effective in maintaining a consistent flow of wood chips, something that was not possible with previous designs that used fixed-position augers. Additionally, the inclusion of a rotating clearing mechanism ensures that the wood chips do not bridge or clump together, further improving the reliability of the fuel delivery system. In addition, the inclusion of an optional auger cover flap reduces backflow of combustion gases. Additionally, in some embodiments the present invention incorporates an advanced switching and programming system that adjusts the auger speed and fuel feed rate based on the type of fuel selected, ensuring consistent combustion performance and preventing jams. This innovation makes the use of wood chips in grills and smokers more practical and safer, and that represents a significant advancement in barbecue technology.

In certain embodiments, a device for delivering and burning combustible material includes a hopper, a burn box to receive and burn the combustible material, an auger tube through which the combustible material is moved from the hopper to the burn box, a motor, and an auger pivotably connected within the auger tube to facilitate adjustment of the auger's orientation within the auger tube in response to irregularly sized or shaped combustible material. In alternative embodiments, the motor includes a drive shaft having an axis of rotation and the auger is pivotably connected to the drive shaft to allow the auger to pivot relative to the drive shaft about an axis substantially perpendicular to the axis of rotation of the drive shaft.

In other embodiments, an apparatus for delivering and burning combustible material includes a hopper to store combustible material, a burn box having an inner volume defined by a sidewall and a bottom wall capable of burning combustible material, an auger tube having an inlet end in communication with the hopper and an outlet end in communication with the burn box, the auger tube suitable for transporting combustible material from the hopper to the burn box, a motor configured to drive the auger, the motor having a drive shaft with an axis of rotation, and an auger positioned within the auger tube, the auger being rotatable about a longitudinal axis to facilitate movement of the combustible material through the auger tube, wherein the auger is pivotably connected within the auger tube to facilitate adjustment of the auger's orientation within the auger tube in response to irregularly sized or shaped combustible material. In alternative embodiments, the auger pivots relative to the drive shaft about an axis that is substantially perpendicular to the axis of rotation of the drive shaft.

In certain other embodiments, a system for delivering and burning combustible material in a cooking appliance including a hopper to store combustible material, an auger tube having an inlet end in communication with the hopper and an outlet end, the auger tube facilitating transport of combustible material from the hopper to the outlet end, an auger positioned within the auger tube, the auger being rotatable about a longitudinal axis to move the combustible material through the auger tube, a burn box having an inner volume defined by a sidewall and a bottom wall, the burn box receives and burns combustible material delivered from the auger tube, a motor with a drive shaft having an axis of rotation, and a pivotable coupling connecting the auger to the drive shaft of the motor, the pivotable coupling enabling the auger to pivot relative to the drive shaft about an axis that is substantially perpendicular to the axis of rotation of the drive shaft, wherein the auger can pivot within the auger tube in response to irregularly sized or shaped combustible material.

In alternative embodiments, the invention includes a cover flap pivotally mounted at an outlet end of the auger tube to cover the outlet end to allow combustible material to exit the outlet end when the auger is rotating with combustible material in the auger tube without allowing combustible material in the auger tube to ignite. In certain embodiments, the invention includes a loop extending through at least two openings in the cover flap, the loop being attached to the auger tube or the burn box, wherein the cover flap is constrained to pivot around the loop in a path that is substantially parallel to the longitudinal direction of the auger tube. In other embodiments, the cover flap lays flat against the outlet end under the force of gravity when the auger is not rotating, thereby preventing combustion gases from escaping into the auger tube, and pivots open when the combustible material is forced through the auger tube by the rotating auger.

In alternative embodiments, the diameter of the auger tube is substantially larger than the diameter of the auger.

In alternative embodiments, at least one pin is rotatably mounted over an opening through which combustible material engages the auger and is oriented substantially perpendicular to the axis of rotation of the auger.

In certain embodiments, the grill incorporates a switching control system that, upon selection, adjusts its internal programming when transitioning between different fuel types. This system modifies both structural and functional parameters, including the speed of the auger, the speed of the fan, and the activation of an agitator, to ensure the optimal fuel feed rate for maintaining the desired British Thermal Unit (BTU) output. The programming is designed to accommodate the differences in burn characteristics between wood chips and pellets, adapting the operation of the grill to match the fuel's specific energy content and combustion behavior. This level of adjustment provides a seamless cooking experience, making the Present invention highly adaptable for various grilling scenarios.

In other embodiments, the invention's switching and programming system operates through an integrated control board that detects the type of fuel being used-whether wood chips or pellets and adjusts the grill's operational parameters accordingly. U pon switching fuel types, the control system automatically reconfigures key components, such as the auger speed, burn box air intake, and hopper agitation, to maintain optimal combustion and achieve the required heat output or BTU. This programming dynamically recalibrates the system based on real-time fuel demands and energy output, ensuring that the grill provides efficient and consistent performance regardless of the fuel type. By automating these adjustments, the system eliminates the need for manual intervention, allowing the user to seamlessly transition between fuel sources while maintaining precise temperature control and fuel efficiency, effectively enhancing the grill's versatility and usability.

Referring to, a cooker, such as a smoker, outdoor grill, or other type of cooker includes a housingdefining a cooking chamber. The cooking chambermay be accessible through an openingthat is selectively covered by a lid (not shown). A grillor other support surface may be positioned within the cooking chamberfor supporting an item cooked within the cooking chamber. A control housingmounted to or near the housingmay contain a hopper, fan, motor, an air chamber, an auger tube, an auger, and a motorfor driving the auger. The control housingmay further house a programable controllercoupled to the motors,and configured to control the motors,, such as in response to the output of a sensor configured to sense the temperature within the cooking chamberand coupled to the programable controller. The programmable controllercan be configured for the type of combustible material being used (wood chips or pellets) and automatically adjust hopper agitation, auger speed, and fan operation to optimize cooking performance based on the selected or detected fuel type, ensuring consistent heat output and efficient fuel consumption. The housingand/or control housingmay be mounted to a framethat itself is mounted on wheelsfor relocating the cooker. The auger tubeand augerextend into the cooking chamberwith a burn box(see) located in and/or under the cooking chamber.

In a preferred embodiment, the hopperincorporates a trap door element at the base of the hopper(not shown) to aid in efficiently removing combustible material if the user elects to switch from the type contained in the hopper. One of ordinary skill in the art would recognize a trap door element could have various dimensions and be placed in multiple locations around the hoppersuch that the force of gravity would cause the combustible material to fall through the trap door and out of the hopper.

The illustrated cookeris exemplary only. Any cooker or heating device using an auger to supply combustible material to be burned may benefit from the invention features described herein.

Referring to, the augermay be formed in a spiral shape around an auger shaft, such as shaft made of steel, aluminum, or other material. The auger shaftis coupled to the motorsuch that the auger shaftcan pivot relative to the motorabout an axis that is substantially (e.g., within 10, 5, or 2 degrees of) perpendicular to the axis of rotation of a motor shaftfrom the motor. For example, the auger shaftmay be coupled to the motor shaftby a pin. Alternatively, the joint between the auger shaftand the motor shaftmay be embodied as a clevis pin link, universal joint, or other type of joint permitting rotation about a first axis while enabling torque transmission about a second axis that is substantially perpendicular to the first axis. In yet another alternative embodiment, a spring wound in the same direction as the rotation of the auger, concentrically connected between the auger and the motor, allows the auger to “float” within the confines of the auger tube in any points in the plane defined by a cross-section of the auger tube.

The hoppercontaining the combustible materialthat may be positioned above the augerand auger tube. The augeris rotated by the motor, causing the combustible materialto be conducted along the auger tubeto the inner volumeof the burn box. The augeris rotated by a motor or manually to drive combustible material from an openingpositioned under the hopperor other source of the combustible material to an outlet end. As is apparent, the outlet endmay be substantially (e.g., within 5 degrees of) perpendicular to the axis of symmetry of the cylindrical auger tube. The axis of symmetry of the cylindrical auger tubemay be substantially (e.g., within 5 degrees of) parallel to the longitudinal directionsuch that the outlet endis substantially parallel to the vertical directionand horizontal direction. Likewise, the axis of rotation of the augermay be substantially parallel to the longitudinal direction

The outlet endis positioned within, or is otherwise in fluid communication with an inner volumeof the burn boxin which combustible material is burned to heat a cooking chamber, grill, or other structure. In the illustrated embodiment, the inner volume of the burn boxis defined by a sidewallhaving and a bottom wallextending across the bottom of the sidewall. The upper end of the sidewallmay be open and may have a mounting platemounted thereto for mounting the burn boxto cooking chamber, housing for a grill, or other structure. In the illustrated embodiment, the sidewallis generally cylindrical with various openings formed therein, with the axis of the cylinder being substantially parallel to the vertical direction. The sidewallmay have one or more vent openingsformed therein. In the illustrated embodiment, louverspositioned adjacent each openingdirect air passing through the openingsinto the inner volumeto spin, thereby cooling the sidewall. The louversmay be formed by bending portions of the sidewallinward. The outlet endmay be positioned closer to the top of the sidewallthan to the bottom wallsuch that combustible material forced out of the outlet endby the augerwill fall onto the bottom walland be burned. The burn boxmay be configured according to any approach for implementing a burn box known in the art. The burn boxmay include an igniter, temperature sensor, fuel sensor, or any other component known to be used with a burn box.

Referring to, in some embodiments, a diameterof the auger tubemay be substantially larger than a diameterof the auger, such as between 5 and 25 percent larger, or between 10 and 15 percent larger. In some embodiments, diameteris at least 0.375 inches larger than the diameter. The difference in diameters,in combination with the joint between the motor and auger shafts,enables the augerto “float.” When using irregularly sized and shaped combustible material(shown with reference to), there may be chunks or clumps of combustible materialthat would tend to jam the auger. Enabling the augerto pivot within an oversized tubereduces the probability of this occurring. Enabling the augerto pivot further enables the combustible materialto include larger chunks, which are cheaper to make. Enabling the augerto pivot further reduces the amount of power required from the motorin order to achieve consistent operation.

In some embodiments, a fuel conditioner may be positioned between the hopperand the auger tubefor grinding wood chips into smaller wood chips or otherwise modifying one or more of the size, shape, or uniformity of the fuel, as described in U.S. Pat. No. 11,940,153, commonly assigned, entitled FUEL CONDITIONER FOR GRILL, which is hereby incorporated herein by reference in its entirety.

A person of skill in the art would understand from the present disclosure that other intermediate elements can be included between the hopperand the burn box. For example, the present invention may use an augeror another form of channel fluidly coupled to the outlet of hopperand the burn box. A channel, such as an auger tube, can have a diameter of, for example, 2.2 inches, 2-2.5 inches, 1.5-3 inches, or any other diameter sized to pass wood chips, which may or may not be pre-conditioned. Whether or not conditioned via an integrated fuel conditioner or pre-conditioned, wood chipsexiting the hopperor fuel conditioner can travel through the channel to the burn boxfor use as fuel. The channel could have a smooth inner surface to facilitate passage of wood chipsto the burn boxby pressure from the hopperor fuel conditioner. A person of ordinary skill in the art would understand from the present disclosure that channel can be sized to ensure that maximum and/or average sized wood chipscan pass through at a rate sufficient to maintain typical and/or maximum desired cooking temperatures within the cooking chamber. And could be equipped with an augerto facilitate or regulate the flow of wood chipsthrough the auger tubeto the burn box.

In some embodiments, the present invention may incorporate a programmable controlled clearing mechanism or agitator an agitator, described below with reference to, or other source of vibration to facilitate the flow of wood chipsfrom the hopperto the burn box.

In some embodiments, described with reference to, an auger cover flapmay be used to reduce combustion of pellets, wood chips, or other combustible material within the auger tubehaving the augerpositioned therein. The auger flapmay be understood with respect to a longitudinal direction, vertical direction, and horizontal directionthat are all mutually perpendicular. The vertical directionmay correspond to the direction of gravity during use.

The auger flapmay be mounted to the auger tube, or to the sidewallby a loop. The loopmay pass through an upper openingdefined by the auger flapand a lower openingdefined by the auger flap. The openings,may be offset from one another along the vertical direction. The lower openingmay be oblong with the long dimension thereof oriented substantially (e.g., within 5 degrees of) parallel to the vertical direction. For example, the long dimension of the lower openingmay be between 1.5 and 4 times the diameter of the upper opening, which may be substantially the same, e.g., within 5% of, the width of the lower openingin the horizontal direction. The diameter of the upper openingand width of the lower openingmay be slightly, e.g., between 1 and 5 percent greater than the width of the loopsuch that the openingsare able to freely slide along the loop.

In the illustrated embodiment, the auger flapincludes a circular portion. The circular portionmay be substantially, e.g., preferably within 3 percent of, equal to the outer diameter of the auger tubeand at least larger than the inner diameter of the auger tubesuch that the auger flapwill not be inducted into the auger tubeduring use. The auger flapmay include a non-circular portion, e.g., a protrusion from the circular portion. The upper openingmay be partially or completely positioned within the non-circular portion. In particular, the size of the loopand position of the upper openingmay be such that at rest and under the action of gravity, the auger flapwill rest flat against the outlet endwith the perimeter of the circular portionsubstantially aligned with the perimeter of the auger tube, e.g., within x*D of aligned along the vertical and horizontal directions,, where D is the diameter of the auger tubeand x is a value less than 0.1, 0.05, or 0.01. The auger flapitself may be formed of a flat plate or other shape such that a surface of the auger flapin contact with the outlet endwill conform to the outlet end. The auger flapmay be made of aluminum, stainless steel, or other type of steel or other metal.

The engagement of the openings,with the loopconstrains the auger flapto pivot around the loop, or cause the loopto pivot within opening, in a rotational paththat is substantially, e.g., within 5 degrees of, parallel to the longitudinal directionand the vertical direction. The use of two openings,rather than a single opening helps avoid movement of the auger flap away from the pathand becoming stuck in an open position.

The auger tubemay itself define an openingwith the looppassing through the opening. The portion of the auger tubedefining the openingmay be positioned within the inner volumeof the burn box. The loopmay be implemented as a piece of metal formed into a ring. The loopmay for example be implemented as a curved or straight material bent into a ring shape passing through the openings,,. The loopmay be free to move within the openingor may be welded or otherwise secured in place relative to the auger tube. The diameter of openingmay be slightly, e.g., between 1 and 5 percent greater than the width of the loopsuch that the ringis able to freely move through the opening.

Referring back toand further with reference to, in some applications, air will be forced into the burn boxthrough openings. In such applications, the air pressure within the burn boxmay urge the auger flapagainst the outlet endof the auger tube. For example, a fandriven by a motormay force air into an air chamberthrough openingsfor receiving ambient air. The air chambermay be extended around the burn boxsuch that air forced into the air chamberwill be forced through the openingsinto the inner volume, urging the openingsto spin via the louvres. In addition, the programmable controllercan adjust the fan speed in response to real-time temperature data or fuel type, optimizing airflow for more efficient combustion based on the material being used, whether wood chips or pellets, to ensure consistent cooking performance.

illustrate the operation of the auger flap. Referring specifically to, when the augeris not rotating and urging combustible material through the tube, the auger flapis suspended from the loopand compelled by gravity to lay substantially flat (e.g., within 2 degrees of flat) against the outlet endof the tube.

Referring specifically to, when combustible materialis forced by the augerthrough the tubeinto the inner volumeof the burn box, the combustible materialwill force the auger flapto pivot about the directionand allow the combustible materialto fall from the outlet endonto the bottom wall, where the combustible materialwill be ignited by currently burning combustible material or an igniter. In some embodiments, the loopitself may pivot upward slightly within the opening. Pivoting of the auger flapmay include the openings,sliding along the loop, with the combined openings,and the offset therebetween maintaining the auger flapwithin a narrow range of motion (e.g., less than 5, less than 2, or less than 1 percent of the diameter of the tube) in the horizontal direction

When the augerstops moving or combustible materialis no longer being forced through the tubeand any combustible material at the outlet endhas fallen into the inner volume, the auger flapwill be compelled by gravity to fall back to the position shown in. The combined openings,and the offset therebetween help guide the auger flapback into the position ofrather than becoming stuck in some other position.

Referring to, when using irregularly sized and shaped combustible material, for example wood chips (either conditioned or unconditioned) it is possible for the combustible materialto “bridge” above the auger. The combustible material may interlock to form a bridge above the augersuch that combustible materialno longer engages the augerand is not fed through the tube. To prevent bridging, a clearing mechanism or agitatormay be used. In the illustrated embodiment, the clearing mechanism is one or more pinsthat rotate over an openingat the bottom of the hopperthrough which the combustible material engages the augerand enters the tube. The pinmay be connected to a clearing shaftthat rotates about an axis of rotation substantially (e.g., within 5 degrees of) parallel to the axis of rotation of the auger. The pinmay be cylindrical and orientated substantially (e.g., within 5 degrees of) perpendicular to the axis of rotation of the clearing shaft. The clearing shaftmay be driven by the motor(see) through one or more gears and may rotate at a same or different speed from the auger. Alternatively, a separate motor (not shown) may drive the clearing shaft. A distal end of the pinmay traverse a pathover the opening. The pathmay pass within 0.25, 0.125, or within 0.0625 inches of the auger. The distance between the axis of rotation of the clearing shaftand the distal end of the pinmay be between 2 and 8 times the diameterof the auger. However, smaller or larger distances may also be used. The programmable controllercan adjust the hopper agitator's operation and the speed of the auger's movement based on real-time monitoring of fuel flow, preventing blockages and optimizing fuel delivery.

Referring to, the programmable controllerregulates the various components of the cookerto adapt to different fuel types, such as pellets, wood chips, and other irregularly sized combustible material, ensuring efficient fuel combustion and consistent heat output. The controlleris configured to manage the operation of the auger, hopper agitator, and fansbased on the type and size of the fuel being used. For instance, when wood chips or irregularly shaped combustible materialare selected, the controllercan adjust the auger's speed and the rotation of the clearing shaftto prevent bridging, while simultaneously adjusting the airflow provided by the fansto maintain optimal combustion conditions within the burn box. Additionally, the programmable system is capable of calculating the required fuel feed rate based on one or more of the real-time temperature readings of the ambient temperature, the temperature within the cooking chamber, and the type of fuel loaded into the hopper, as different fuels produce varying BTU outputs. For example, pellets may provide a higher BTU per pound compared to wood chips, which require a higher feed rate to maintain consistent temperatures. In some embodiments, sensors within the hopperand burn box, together with the controller, can dynamically adjust the auger's feed rate to ensure the correct amount of fuel, air, is delivered to produce the required BTU content, compensating for changes in fuel type or size without user intervention. This adaptability enables the cookerto operate efficiently across a variety of fuel sources, ensuring consistent cooking performance regardless of the fuel type used.

To account for variations in ambient temperature, fuel moisture, etc., a preferred embodiment of the present invention incorporates a Proportional Integral Derivative (PID) controller that compares the target temperature set by the user to the actual temperature in the cooking chamberto calculate the proportional difference in temperature, the cumulative sum of past temperature error (the integral of the temperature error), and the rate of change of the difference between the target temperature and the actual temperature (the derivative of the temperature error).

Depending on the nature of the temperature error calculations determined by the PID, the programable controller may adjust the speed of fuel and air inputs to dynamically maintain the target temperature without adjusting the input too rapidly, which could result in the combustion in the firebox to be extinguished. In the event the programable controller detects the fire has been extinguished based on direct sensor readings, or calculations from the PID, a preferred embodiment of the present invention may be configured to activate the ignitor to reignite combustible material in the burn box.

Referring to, a preferred programmable controllerserves as the central hub for managing the present invention's operations and user interface. It includes a fuel type selector, allowing the user to choose between using wood chips or wood pellets, ensuring the variable fuel cooker adjusts its auger speed and airflow to optimize combustion and cooking temperature based on the selected fuel. A wireless connectivity antennaenables WiFi or Bluetooth connectivity, allowing remote control and monitoring of the grill's performance via a dedicated application on a remote communication or computing device, such as a mobile device, notebook, tablet, wearable or similar technology. A display screenprovides real-time feedback on the grill's status, including temperature, fuel type, and other system settings.

The controller also preferably includes a probeselectorand a probeselector, which allow the user to display and manage the temperature readings from a wireless thermometer probethat communicates with the cooker. Multiple wireless thermometer probescan be paired to the cooker through a probe input slot, which is also designed to securely store the probe when not in use. A temperature selectorsallow precise adjustment of the grill's target cooking temperature, while a temperature unit selectorprovides the option to switch between Celsius and Fahrenheit units. Finally, the controller may be operated by an on/off switch, providing easy power control for the entire system.

The controller or other part of the system (e.g., control housing) disclosed in the present invention further includes one or more microprocessors (not shown) coupled to or otherwise configured to actuate or control one or more system components, such as the hopper, fan, motors,, air chamber, auger tube, auger, and agitatorusing instructions that are predetermined or dynamically established based on fuel type characteristics and other grill operation variables, as further described with reference to.

is a flow diagram of a process for operating the present invention based on fuel type selection according to some embodiments. The process begins at block, where system receives an indication of a user selection of fuel type, either pellets or wood chips. Prior to or at the time of this operation, the user will have filled the hopperwith a predetermined and desire fuel type. This indication may be based on a manual entry by the user, for example via the fuel type selector. In alternative embodiments, the system may include one or more fuel type sensors (e.g., camera, scale, or other fuel type assessment device) that determine fuel type currently in the hopperbased on size, shape or other characteristic of the fuel. If pellets are selected, a Pellets program is activated at blockand at block, pellets are dispensed from the hopper, through the augerfor a time of x seconds at y rpm and delivered to the burn boxat block. The time and rate of the augermay vary based on, as examples only, the size of the cooking chamberor the ambient temperature. If chips are selected a Chips program is activated at block, activating the clearing mechanism at block, and chips are dispensed from the hopperthrough the augerfor a predetermined time of between 1.5× and 2.25×, or preferably (based on testing) 1.89× seconds at y rpm, or a time of x seconds at a rate of 1.89 rpm, and delivered to the burn boxat block. The 1.89 multiple is optimized for commercially available chips, but may be adjusted to account for the relative density of various wood chips as measure by either the BTU content of the selected combustible material or the weight of the selected combustible material when accounting for the material's moisture content.

At block, an ignitor in the burn box, and fan, feeding air into the burn box is activated to initiate combustion of the selected fuel. At block, the cooker reads the temperature selectorsetting, and at blockcollects temperature sensor data from the cooking chamber. If the temperature selectorsetting does not align with the sensor data collected from the cooking chamber, at block, the system adjusts the rate of fuel delivery through the augerto the burn box, and/or the rate of air flow delivered to the burn boxby the fan, to maintain the selected temperature. If the temperature in the cooking chamberis too low the rate of fuel and air delivery to the burn boxmay be increased. And if the temperature is too high, the rate of fuel and air delivery to the burn boxmay be decreased.

In a preferred embodiment, when the fuel type selectoris triggered by the user at block, the programable controller will maintain the prior rate of fuel delivery to the burn boxfor approximately 3 minutes, or until the augerhas completed sufficient rotations to fully dispense combustible material retained in the auger tube, prior to engaging either the newly selected Pellets program at, or the newly selected Chips program at. In other embodiments the calculations from the PID controller will cause the programable controller to dynamically adjust the feed rate of combustible material until the prior fuel contained in the auger tubehas been dispensed to the burn boxand replaced by the newly selected fuel type contained in the hopper.

Various methods exist for calculating BTU content for different fuels, including based on weight or volume. For example, one pound of hardwood pellets, or about 0.025 cu ft of pellets, adjusted for moisture content, produces about ˜7,900 BTUs. One pound of hardwood chips, or about 0.043 cu ft of chips, adjusted for moisture content, produces about 7,300 BTUs. An alternative embodiment of the present invention may incorporate a scale or volume measurement feature in the hopper that weighs or measures fuel before moving it into the auger and subsequently the burn box, and the rate can be calculated based on such measurements.

The maximum size of the chip is a mathematical function of the auger tube diameter, auger diameter, pitch (distance the product moves during one revolution of the auger), and motor torque. In one example, the largest chip a 2 inch diameter auger tube could accommodate would theoretically be 1.99999 inches, but the motor torque required to move this through the tube would be astronomical. After experimentation, it was determined that a 25 nm (newton-meter or 18.44 ft-lbs.) motor will reliably deliver chips as large as ¾ inch diameter through a 2 inch diameter auger tube to the burn box. However, it should be understood that different auger tube sizes may be used depending on the specific fuel characteristics.

In a preferred operation of the present invention, wood chips are dried to below 20% moisture content, and preferably about 15% moisture content, in order to let the steam produced when burning the wood chips to permeate the food and condition it to a much moister result. This 15% moisture content is well below the “mold threshold” of between 20% and 27%, which is generally understood to be a range that is safe from fungal infection. Accordingly, the optimum rate for dispensing fuel is in part a function of the moisture content of the fuel. For example, if for wood chips the moisture content is 0% (meaning the chips are 100% dry), a preferred rate may be 1.76× seconds at y rpm, or a time of x seconds at a rate of 1.76 rpm, instead of 1.89× if the moisture content is 15%. Note that a different rate will still work (for example 1.76× used with 0% moisture content), although it would take longer to reach the desired temperature.

The controller calculates the quantity of fuel needed by starting with which fuel type selected—Pellets or Chips. Pellets produce ˜183 BTUs per cubic inch. Wood chips produce ˜97 BTUs per cubic inch. A typical 30,000 BTU pellet grills (this means 30,000 BTUs per hour) will need to put 164 cubic inches of pellets per hour (2.73 cu. in. per minute) or 309 cubic inches of wood chips per hour (5.14 cubic inches per minute) into the burn box, ignoring ambient temperatures. Colder ambient temps will require increased BTUs, as hotter ambient temperatures will require decreased BTUs. The standard measurements of BTUs for any combustible are done at 20° C. (68° F.), so variations from this temperature will result in lower or higher BTU production. For this reason, a preferred embodiment includes a sensor that measures ambient temperature, and the system adjusts the fuel and air flow rate depending on the measured ambient temperature. The number of turns of the auger and the RPM s necessary to transport the required amount of fuel into the burn box is readily calculated once ambient temperate and fuel type are known. Accordingly, the sensor, reading the AT (Actual Temperature) information, will feed this information to the controller, which will adjust (for now anyway) the feed rate proportionally (mathematically) to attain the desired temperature. Of course, there are guiderails, as this rate cannot be so high as to pack the burn box with fuel, which would extinguish the fire.