Patent Description:
Embodiments herein relate to the field of lumber drying, and, more specifically, to methods and systems for drying wood products in a kiln with at least two generally parallel flow paths along which charges are moved through the kiln in substantially the same direction of travel.

Green lumber is typically stacked, grouped in batches, and dried batch-wise in a kiln. The batches of lumber ("charges") are placed within an insulated chamber in the kiln, and the chamber is closed. Conditions within the chamber (e.g., air temperature, air flow direction/speed, and humidity) are set according to predetermined parameters, which may vary according to various factors such as lumber type, lumber thickness, and the starting moisture content of the lumber. The lumber is dried within the chamber for a predetermined length of time or to a predetermined moisture content. The moisture released by the lumber into the surrounding air is vented to the external surroundings. The insulated chamber is then opened to remove the dried lumber and to insert the next batch of green lumber. This exchange allows heated air and moisture to escape, requiring a readjustment of the temperature and other conditions within the chamber between successive batches of lumber.

<CIT> discloses a timber drying kiln with multiple chambers, in which different conditions are maintained in each chamber. Timber is preheated in one chamber, rapidly heated within the next chamber, transferred to another chamber for further drying, and then transferred to a conditioning chamber.

According to an aspect of the present invention, there is provided a lumber drying system as defined in the claims.

According to another aspect of the present invention, there is provided a method of heat treating lumber using the above lumber drying system, as defined in the claims.

In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration embodiments that may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of embodiments is defined by the appended claims and their equivalents.

Various operations may be described as multiple discrete operations in turn, in a manner that may be helpful in understanding embodiments; however, the order of description should not be construed to imply that these operations are order dependent.

The description may use perspective-based descriptions such as up/down, back/front, and top/bottom. Such descriptions are merely used to facilitate the discussion and are not intended to restrict the application of disclosed embodiments.

The terms "coupled" and "connected," along with their derivatives, may be used. Rather, in particular embodiments, "connected" may be used to indicate that two or more elements are in direct physical or electrical contact with each other. "Coupled" may mean that two or more elements are in direct physical or electrical contact. However, "coupled" may also mean that two or more elements are not in direct contact with each other, but yet still cooperate or interact with each other.

The description may use the terms "embodiment" or "embodiments," which may each refer to one or more of the same or different embodiments. Furthermore, the terms "comprising," "including," "having," and the like, as used with respect to embodiments, are synonymous.

In various embodiments, methods, apparatuses, and systems for drying lumber products are provided. In exemplary embodiments, a computing device may be endowed with one or more components of the disclosed apparatuses and/or systems and may be employed to perform one or more methods as disclosed herein.

Lumber is typically dried in a kiln to reduce the moisture content of the wood to within an acceptable range. Lumber loses or gains moisture until reaching an equilibrium moisture content (EMC). The EMC is a function of the temperature and relative humidity of the surrounding air - as the temperature increases and/or the relative humidity decreases, the EMC decreases and the lumber loses additional moisture. Therefore, the moisture content of lumber can be decreased by adjusting temperature and humidity within the kiln. However, sudden changes in these conditions can cause the outer surfaces of the lumber to dry and shrink more rapidly than interior portions, resulting in cracks and warping.

Some mills have begun to dry lumber in continuous kilns. Conventional continuous kilns include a central heating zone with a preheating zone at the proximal end and a cooling zone at the distal end. The preheating and cooling zones are typically of equal length, and are typically <NUM> to <NUM>% of the length of the central heating zone. Two parallel paths extend through the three zones, and lumber charges are conveyed through the kiln along one path or the other. Typical lengths for the heated chamber range from <NUM> ft to <NUM> ft, and each of the unheated chambers adds another <NUM>-<NUM>% of that length. The rate at which lumber charges are transported through the heated chamber depends in part on the length of the heated chamber. One foot is equal to <NUM> centimeters (cm).

<CIT> discloses a dual path lumber kiln in which lumber flows through three zones (two unheated end zones and a heated middle zone) along one of two opposing paths with opposite directions of flow. Each end of the kiln includes the exit portal of one path and the entry portal of the other path. As dried lumber exits the drying chamber and proceeds toward the exit on one path, green lumber is traveling toward the drying chamber on the other path. The green lumber is gradually preheated by heat released by the dried lumber, and also by the condensation of water vapor (steam) from the drying chamber, which effects a transfer of energy to the lumber. In turn, the moisture released into the air by the preheated green lumber (and by the drying chamber) serves to condition the dried lumber as it cools.

This dual path counter-flow design requires a relatively large footprint. In addition to the length added by the unheated sections extending from both ends of the heated section, space must also be reserved for stacking dried lumber or green lumber at both entrances and exits.

The present disclosure provides embodiments of a dual-path unidirectional kiln. Such kilns may have a number of advantages over prior kiln designs. First, dual-path unidirectional kilns as described herein may have a comparatively smaller footprint than prior kilns. Dual-path unidirectional kilns may also have lower construction costs, better drying efficiency, and/or lower costs of use (e.g., lower energy costs). In addition, embodiments described herein can be used with a simpler and more convenient transport system. A dual-path unidirectional kiln may optionally use one device to move lumber charges along both sides of the kiln simultaneously, whereas prior designs require at least one such device for each side of the kiln. A dual-path unidirectional kiln also allows all of the lumber charges to enter at the same end, and to exit at the same end, making the handling and transport of the green and dry lumber simpler and more efficient. Such kilns can be used with simpler rail/track systems than are required for conventional counter-flow kilns. This allows a lumber mill to have a direct input path from a lumber stacker to the input end of the kiln, and a direct path from the output end of the kiln to a planer mill or other destination.

In one embodiment, a kiln may include an unheated chamber coupled to a heated chamber to form a continuous enclosure with two charge portals in or near the unheated chamber and two exit portals at the opposite end of the continuous enclosure. Optionally, a third chamber may be coupled to the distal end of the heated chamber. Two substantially parallel flow paths may extend through the continuous enclosure, and lumber charges may be conveyed through the enclosure along one or the other of the flow paths. Embodiments with a third chamber may include an additional set of exit portals that can be opened and closed to reduce heat and steam loss through the distal end of the unidirectional kiln.

The term "flow path" is defined herein as a path along which a movable support for a lumber charge travels through a kiln. In a dual-path unidirectional kiln, two substantially parallel flow paths may extend, on opposite sides of a longitudinal axis, from an entrance at a proximal end of the kiln to an exit at a distal end of the kiln. Lumber charges may be conveyed along the parallel flow paths in substantially the same direction of travel.

<FIG> illustrate perspective views of embodiments of a dual-path unidirectional kiln. Kiln <NUM> may include a first chamber <NUM> coupled to a second chamber <NUM> to form an elongated enclosure. Kiln <NUM> may also include a support surface <NUM>, guide members <NUM>, and one or more transport assemblies <NUM>. In the illustrated embodiment, at least one transport assembly <NUM> is provided along each of two flow paths.

The dimensions of first and second chambers <NUM> and <NUM> can vary among embodiments. In conventional continuous flow kilns, the end sections are commonly about <NUM>% of the length of the central heated chamber. In contrast, some embodiments of a unidirectional dual-path kiln may have end sections (first chamber <NUM>/third chamber <NUM>) that are shorter than in conventional kilns. Closing the distal end of the kiln may help to concentrate heat and steam in first chamber <NUM>, allowing first chamber <NUM> to pre-heat/condition lumber more efficiently than in conventional kilns. Thus, in some embodiments, first chamber <NUM> may be <NUM>-<NUM>%, <NUM>-<NUM>%, or <NUM>-<NUM>% of the length of second chamber <NUM>. However, in other embodiments, first chamber <NUM> may be <NUM>-<NUM>% or <NUM>-<NUM>% of the length of second chamber <NUM>. Typically, first chamber <NUM> has a length of <NUM> to <NUM> feet, <NUM> to <NUM> feet, <NUM> to <NUM> feet, or <NUM> to <NUM> feet. However, first chamber <NUM> can have any suitable length. One foot is equal to <NUM> centimeters (cm).

The length of second chamber <NUM> can be <NUM> to <NUM> feet, <NUM> to <NUM> feet, <NUM> to <NUM> feet, <NUM> to <NUM> feet, <NUM> to <NUM> feet, <NUM> to <NUM> feet, or <NUM>-<NUM> feet. Optionally, second chamber <NUM> may be a pre-existing kiln or portion thereof. In a particular embodiment, first chamber <NUM> has a length of <NUM> to <NUM> feet and second chamber <NUM> has a length of <NUM> to <NUM> feet. The chambers may be joined end-to-end to form a continuous enclosure. Some embodiments may include one or more internal walls or baffle within a chamber or between two chambers to control heat exchange between adjacent areas.

One foot is equal to <NUM> centimeters (cm).

As shown in <FIG>, <FIG>, and <FIG>, some kilns may include a third chamber <NUM> coupled to second chamber <NUM>. Optionally, third chamber <NUM> may be provided with one or more fans and/or heaters. Third chamber <NUM> may have a length that is equal to, or less than, the length of first chamber <NUM>. For example, the length of third chamber <NUM> may be <NUM> to <NUM> feet, <NUM> to <NUM> feet, <NUM> to <NUM> feet, <NUM> to <NUM> feet, <NUM> to <NUM> feet, or <NUM> to <NUM> feet. Third chamber <NUM> may be dimensioned to accommodate a single lumber charge of a standard length, or two or more lumber charges. In a particular embodiment, the sum of the lengths of first chamber <NUM> and third chamber <NUM> is less than the length of second chamber <NUM>. In another embodiment, the combined lengths of the chambers is <NUM> to <NUM> feet (i.e., linear distance from the proximal end of first chamber <NUM> to the distal end of the most distal chamber of the kiln). Third chamber <NUM> may have the same or similar width as second chamber <NUM>. Alternatively, as shown in <FIG>, third chamber <NUM> may be a pair of smaller chambers (140a and 140b).

Support surface <NUM> may form the floor of kiln <NUM>. Optionally, support surface may extend beyond first chamber <NUM> and/or second chamber <NUM>. Support surface <NUM> can be constructed from concrete or any other type of material suitable for use in a lumber kiln.

Guide members <NUM> may be coupled to support surface <NUM>. Guide members <NUM> can include one or more tracks, guide members, and/or rails. Guide members <NUM> may be mounted to, and/or at least partially embedded in, support surface <NUM>. In some embodiments, a guide member <NUM> or another guide member may be provided above or beside a flow path.

One or more movable supports <NUM> (see <FIG>) may be coupled to guide member(s) <NUM>. Movable support <NUM> may include a support surface coupled to one or more rotatable members. For example, movable support <NUM> may include a platform <NUM> mounted on guide member couplers <NUM> that are configured to engage the top/side of guide member <NUM>. Guide member couplers <NUM> can be rotatable members (e.g., wheels), rigid or slideable members (e.g., pins), or other elements known in the art for movably coupling a platform to a rail, track, or the like. In any case, guide members <NUM> may guide the movable supports along the first and second flow paths through the kiln. Therefore, guide members <NUM> may define the first and second flow paths or portions thereof.

Transport assembly <NUM> may be coupled to movable support <NUM> and/or to guide member <NUM>. Transport assembly <NUM> may be disposed over, under, or next to guide member <NUM>. Transport assembly <NUM> can be any mechanism or device configured to push or pull one or more movable supports <NUM> along a flow path. In some embodiments, transport assembly <NUM> may include a motor or a pulley/winch coupled to movable support <NUM>. In other embodiments, transport assembly <NUM> may be coupled to guide member <NUM>. For example, the motive force mechanism may include an endless loop (e.g., a chain or belt mounted on sprockets/wheels) that extends between the first and third portions of guide member <NUM>. Movable supports <NUM> may be connected to the endless loop, which may be driven to transport the lumber charges through the kiln along guide member <NUM>.

Optionally, transport assembly <NUM> may be a pusher device as described in <CIT>. Essentially, this pusher device is configured to travel along a track that includes two parallel rails and a chain extending between the rails. The pusher device includes a frame with a front-mounted vertical plate, axle supports, transverse support struts, and rotatably-mounted toothed gears. An axle is mounted to the frame via the axle supports, and the transverse support struts support a variable speed electric motor. A large wheel and two pulleys are mounted on the axle. The output of the electric motor is connected to the large wheel by a chain or belt. The electric motor rotates the wheel, the wheel transmits motion to the axle, the axle rotates the pulleys, and the pulleys transmit rotary motion to the toothed gear(s). The toothed gear(s) engage a link chain positioned between two rails. Rotation of the toothed gears while engaged with the link chain propels the pusher device along the pair of rails. A cable connects a source of current to the electric motor, and is carried and tensioned on a spool rotatably mounted to the housing.

Lumber may be placed onto movable support <NUM>, and movable support <NUM> may be pushed, pulled, or otherwise moved in the direction of flow by transport assembly <NUM>, and guided through the kiln along a flow path by guide member <NUM>. In some embodiments, a single transport assembly <NUM> may be used to push movable supports <NUM> along both flow paths (see e.g., <FIG>). In these embodiments, transport assembly <NUM> may be coupled to guide members <NUM> of both flow paths. Alternatively, transport assembly <NUM> may be coupled to other guide members, such as a central track, rails, carriage, or the like. Optionally, transport assembly <NUM> may push two movable supports, one on each flow path, simultaneously toward/into kiln <NUM>. In other embodiments, each flow path may be provided with a separate transport assembly <NUM>.

Referring now to <FIG>, <FIG>, <FIG>, and <FIG>, first chamber <NUM> may have a first charge entry portal 112a and second charge entry portal 112b. In these embodiments, first charge entry portal 112a may be an entry portal for charges proceeding into kiln <NUM> along first flow path <NUM>, and second charge entry portal 112b may be an entry portal for charges entering kiln <NUM> along second flow path <NUM>. Likewise, first charge exit portal 114a may be an exit portal for charges exiting kiln <NUM> along first flow path <NUM>, and second charge exit portal 114b may be an exit portal for charges exiting kiln <NUM> along second flow path <NUM>. In some embodiments, the only venting of the kiln is through the charge portals <NUM> and <NUM>. In other embodiments, one or more vents may be provided in first chamber <NUM> and/or third chamber <NUM> to controllably regulate the temperature and manage any condensation or moisture congregation that may occur.

Alternatively, as shown in <FIG>, <FIG>, <FIG>, and <FIG>, first chamber <NUM> may have a width that is substantially half the width of second chamber <NUM>. In such embodiments, first chamber <NUM> may include one of the entry portals <NUM> and the other entry portal <NUM> may be provided in or near the proximal end of second chamber <NUM>. In this configuration, lumber charges that require relatively more drying time or preheating may be routed along the flow path that passes through first chamber <NUM>, and other lumber charges that require relatively less drying time or preheating may be routed along the other flow path that does not pass through first chamber <NUM>.

<FIG> show examples of flow paths within unidirectional multi-path kilns. Guide members <NUM> may define the flow paths (e.g., where guide member <NUM> includes tracks or rails along support surface <NUM>). Therefore, the following description of flow paths may also apply to corresponding guide members <NUM>. In the illustrated examples, first flow path <NUM> may extend through a first side of the kiln from a first charge entry portal 112a to a first charge exit portal 114a. Likewise, a second flow path <NUM> may extend through an opposite second side of the kiln from a first charge entry portal 112b to a first charge exit portal 114b. The first and second flow paths <NUM>/<NUM> may be substantially parallel and on opposite sides of a longitudinal axis <NUM> of second chamber <NUM>. Lumber charges may be conveyed along the first and second flow paths in the same direction of travel (Arrows A and B).

Some embodiments may include more than two flow paths. For example, a unidirectional multi-path kiln can have three, four, five, or more than five flow paths arranged in parallel. Again, a single transport assembly <NUM> may be used to move lumber charges along each path simultaneously. Alternatively, two or more transport assemblies may be provided.

Embodiments with a third chamber <NUM> may have intermediate charge portals 124a and 124b positioned between second chamber <NUM> and third chamber <NUM>. Intermediate charge portals 124a/124b may be provided with one or more insulating members (e.g., a door) that are selectively actuable to open as a lumber charge reaches the distal end of second chamber <NUM> and passes into third chamber <NUM>, and to close again once the lagging end of the lumber charge has entered third chamber <NUM>. This may minimize the passage of heat/steam from second chamber <NUM> to third chamber <NUM> and/or through charge exit portal 114a/114b. In a particular embodiment, one or more sensors may be provided along a flow path to detect a position of a lumber charge, and a computing system receiving data from the sensors may control operation of any or all of the charge portals based on sensor data and other factors (e.g., drying schedule, conditions within the drying chamber, rate of lumber charge travel, etc.) This may improve energy efficiency and/or aid in the flow of moist heated air from second chamber <NUM> to flow toward chamber <NUM>. Alternatively, intermediate charge portals 124a/124b may be provided with an insulating member configured to be pushed aside by the passage of a lumber charge (e.g., a polymer curtain, a vertical strip curtain, or swinging doors).

As shown for example in <FIG>, third chamber <NUM> may be a pair of smaller chambers added to the distal end of second chamber <NUM>. Again, third chambers 140a/140b may be sized to accommodate a single lumber charge of a standard size, or any number/size of lumber charges. Optionally, charge exit portals 114a/114b may be selectively actuable to open as a lumber charge reaches the distal end of third chamber <NUM>, and to close again once the lagging end of the lumber charge has exited third chamber <NUM>. Alternatively, charge exit portals 114a/114b may be selectively actuated or controlled by a computing system as described above for intermediate charge portals 124a/124b. As another alternative, charge exit portals 114a/114b may be selectively actuated or controlled to open and/or close once a predetermined length of time has elapsed after opening/closing intermediate charge portals 124a/124b. In some embodiments, charge exit portals 114a/114b may be provided with an insulating member configured to be pushed aside by the passage of a lumber charge as described above.

<FIG> illustrate more detailed plan views of the kilns of <FIG>, in accordance with various embodiments. In these examples, chamber <NUM> includes subsections 10a and 10b, chamber <NUM> includes subsections 12a, 12b, 12c, and 12d, and chamber <NUM> (<FIG>) includes subsection <NUM>. Fans <NUM> may be provided in some or all of the chambers/subsections and positioned to circulate air around the lumber charges. Fans <NUM> may be coupled to corresponding drives <NUM>. In some embodiments, a third chamber <NUM> may lack a fan and corresponding drive.

Some chambers, sections, or subsections may optionally be separated by one or more baffles <NUM> (indicated by broken lines). Baffles <NUM> may reduce the loss of heat and steam from the kiln by reducing the migration of moist, heated air between adjacent subsections (e.g., reduce migration of air from subsection 10b to subsection 10a). This may increase the efficiency of pre-heating/cooling and aid temperature regulation in adjacent chambers/subsections by minimizing fluctuations in temperature within those areas. Minimizing temperature fluctuations and reducing the migration of moisture between adjacent subsections may allow the green lumber to be pre-heated/cooled at a selected optimal rate, which may help to reduce or prevent defects from overly rapid drying or cooling of the lumber. Other embodiments may include additional subsections, fewer subsections, or no subsections.

Subsections 10a and 10b may include subsections one or more fans <NUM> positioned to circulate air and steam received from chamber <NUM> around lumber charges proceeding through first chamber <NUM>, a first preheat side that includes charge entry portal 112a, and a second preheat side that includes charge entry portal 112b. Within first chamber <NUM>, fans <NUM> may circulate air across green lumber charges progressing in the same direction along the two flow paths toward the exit portals 114a/114b. In other embodiments, first chamber <NUM> (e.g., subsections 10a and 10b) may have only one preheat side and the corresponding charge portal (<FIG>, <FIG>). In either case, fans <NUM> may circulate air across the lumber charges to preheat the lumber.

Subsections 12a, 12b, 12c, and 12d of second section <NUM> may be supplied with heated air by a fan and duct system <NUM> coupled to a heater <NUM>. Any or all of subsections 12a-d may include heating members, such as a vertical booster coil assembly between the first and second sides and/or heating coils extending horizontally near fans <NUM>, to maintain or increase the temperature of the circulating air. Optionally, one or more heating members may be provided in first chamber <NUM> and/or third chamber <NUM>. These heating members may be selectively controlled to maintain a desired temperature within a chamber, section, or subsection, or a desired temperature differential between adjacent chambers, sections, or subsections.

The influx of heated air and the higher temperatures within section <NUM> may result in a pressure differential between section <NUM> and the entry charge portals 112a/112b. The entry, exit, and intermediate charge portals may be the primary, or the only, source of ventilation in kiln <NUM>. Thus, in embodiments with intermediate portals/insulated charge exit portals, the pressure differential may enhance the flow of heat and moisture from second chamber <NUM> toward the proximal end of first chamber <NUM> and reduce the flow of heat and moisture in the opposite direction (i.e., from second chamber <NUM> toward the distal end of kiln <NUM>). This design may provide more efficient preheating of lumber than in prior continuous kilns.

Optionally, fans <NUM> may be reversible fans configured to rotate in two opposite rotary directions. Likewise, drives <NUM> may be reversible drives (i.e., configured to drive fans <NUM> in two opposite rotary directions). However, because of the pressure gradient and unidirectional flow path, fans <NUM> and/or drives <NUM> may be unidirectional instead of reversible. Using unidirectional fans/drives may reduce costs and/or energy use associated with operating kiln <NUM>.

In one embodiment, fans <NUM> within second chamber <NUM> and/or third chamber <NUM> may be operated at a greater rotational speed than fans within first chamber <NUM>. As a result, the velocity of circulating air may be greater in second chamber <NUM> and/or third chamber <NUM> than in first chamber <NUM>. The air velocity may be progressively reduced among subsections nearer to the charge entry portals 112a/112b.

In operation, a first stack of green lumber is placed on a movable support <NUM>, and a transport assembly <NUM> pushes or pulls movable support <NUM> into a first end of kiln <NUM> either through first charge portal 112a and along first flow path <NUM>, or through second charge portal 112b and along second flow path <NUM>. Green lumber passing through first chamber <NUM> is pre-heated by steam flowing from second chamber <NUM> as the corresponding movable support(s) <NUM> proceeds toward second chamber <NUM>.

The green lumber is heated and continues to lose moisture as the green lumber charges on movable supports <NUM> proceed through second chamber <NUM>. In some embodiments, the first and second sides of second chamber <NUM> may be divided by a wall or other structure that reduces direct airflow from the first side to the second side. Optionally, one or more heaters may be provided within second chamber <NUM> to increase air temperature/pressure. In other embodiments, second chamber <NUM> may lack heaters and/or a longitudinal dividing structure.

In some embodiments, the dried lumber charges may exit second chamber <NUM> through exit charge portals 114a/114b. In other embodiments, the dried lumber charges may proceed from second chamber <NUM> into third chamber <NUM>. Optionally, the lumber charges may pass through intermediate charge portals 124a/124b provided between second chamber <NUM> and third chamber <NUM>. The temperature within third chamber <NUM> may be lower than the temperature within second chamber <NUM>. This may allow the green lumber to reach a more uniform temperature or moisture content (e.g., reduce the difference between the outer surface temperature/moisture and interior temperature/moisture). Third chamber <NUM> may be provided with one or more fans <NUM> positioned to circulate air around the lumber.

The travel time of the lumber charges may vary depending on various factors. Lumber charges traveling along one flow path may be moved through the kiln at a faster rate than lumber charges traveling along another flow path. The movable supports may be moved along a flow path at a predetermined rate (e.g., <NUM>-<NUM> feet/hour, <NUM>-<NUM> feet/hour, <NUM>-<NUM> feet/hour, or <NUM> feet/hour). Lumber charges on movable supports may be moved continuously through the kiln along the flow paths. Alternatively, the charges may be moved discontinuously along the flow paths. This could be accomplished by moving the movable supports a desired distance, pausing for an interval of time, and moving the movable supports another desired distance. The distances may be incremental (e.g., increments of <NUM>-<NUM> feet, <NUM>-<NUM> feet, <NUM>-<NUM> feet, <NUM> foot, <NUM> feet, etc.).

One foot is equal to <NUM> centimeters (cm). One foot per hour (ft/h) is equal to <NUM> meter per second (m/s).

In some embodiments, a lumber charge may be moved a greater distance or at a faster rate along one portion of the flow path than along another. In a specific example, a lumber charge may be moved continuously or incrementally within second chamber <NUM>. With the leading end of the lumber charge positioned at the distal end of second chamber <NUM>, the lumber charge may be moved into third chamber <NUM> without pausing until the lagging end of the lumber charge has entered third chamber <NUM>. Thus, when the leading end of a <NUM>-foot lumber charge reaches the distal end of second chamber <NUM>, the lumber charge may be moved continuously over a distance of, or in a single increment of, <NUM>-<NUM> feet until the lagging end exits second chamber <NUM>. The lumber charge may be moved at a faster rate along this portion of the flow path than other portions of the flow path in order to reduce the migration of moist heated air from second chamber <NUM> to third chamber <NUM>. Similarly, lumber charges positioned at or near a charge exit portal 114a/114b may be moved through the charge exit portal continuously and/or at a relatively greater speed than the speed of travel through second chamber <NUM>.

The moisture content of the lumber charges may be monitored as the charges progress through the kiln. The rate at which the lumber charges are moved through the kiln and conditions within the chambers/subsections may be adjusted by a computing system based on factors such as initial moisture content of the lumber, humidity, temperature/pressure within a chamber, fan speeds, velocity of air flow, external ambient temperature/humidity, lumber species, lumber dimensions, desired moisture content, and/or input by a human operator.

<FIG> is a flow diagram of a method for converting an existing kiln to a unidirectional multi-path kiln, in accordance with various embodiments.

In some embodiments, method <NUM> may begin at block <NUM>. At block <NUM>, a first chamber (e.g., chamber <NUM>) may be coupled to one end of an existing kiln (e.g., second chamber <NUM>) to form an elongated enclosure with entry charge portals (e.g., charge portals 112a/112b) at a proximal end of the elongated enclosure. Corresponding exit charge portals (e.g., charge portals 114a/114b) may be provided at an opposite distal end of the elongated enclosure. At block <NUM>, one or more guide members (e.g., guide member <NUM>) may be installed within the elongated enclosure. The guide member(s) may be, but is not limited to, tracks, rails, or other such features. The guide member(s) may define two or more paths of flow (e.g., paths <NUM>, <NUM>) through the elongated enclosure from the entry charge portals to the exit charge portals.

At block <NUM>, a movable support/member (e.g., movable support <NUM>) may be coupled to the guide member. In some embodiments, the movable support member may be configured to convey a lumber charge along the guide member.

At block <NUM>, a transport device (e.g., transport assembly <NUM>) may be coupled to the movable support member or the guide member. The transport device may be configured to advance the movable support along the guide member. In some embodiments, the transport device may include a pusher device, a motor, and/or a pulley/winch. Some embodiments may include two or more transport devices, with each of the transport devices positioned along each of the paths of flow (see e.g., <FIG>). Optionally, a single transport device may be provided along or between paths of flow, and may be configured to move lumber charges along multiple flow paths (see e.g., <FIG>).

Optionally, at block <NUM> a second chamber may be coupled to the opposite end of the existing kiln (e.g., third chamber <NUM>). In some embodiments, at block <NUM> a plurality of sensors may be provided along the guide member. The sensors may be operable to detect a position of the movable support member. In one embodiment, at block <NUM> a computing system may be coupled with the sensors. The computing system may be operable to determine, based at least on position data received from the sensors, a current location or travel speed of a lumber charge within the elongated chamber. In other embodiments, any or all of blocks <NUM>, <NUM>, and <NUM> may be omitted.

<FIG> is a flow diagram of a method for operating a unidirectional multi-path kiln, all in accordance with various embodiments. In some embodiments, method <NUM> may begin at block <NUM>. At block <NUM>, an elongated kiln may be provided. The elongated kiln may include a first chamber (e.g., chamber <NUM>), a second chamber (e.g., chamber <NUM>), a charge entry portal (e.g., 112a/112b) and a charge exit portal (e.g., 114a/114b), and two or more flow paths (e.g., <NUM>, <NUM>) that extend through the kiln from the charge entry portals to the corresponding charge exit portals. In some embodiments, intermediate charge portals (e.g., 124a, 124b) may be provided between the second chamber and the third chamber (e.g., third chamber <NUM>). The intermediate charge portals may be provided with insulating members and/or with doors that are selectively actuable to open and close as lumber charges pass through the distal end of the second chamber and into the third chamber.

At block <NUM>, lumber charges may be moved along the flow paths. In some embodiments, two groups of lumber charges may be moved along corresponding ones of the flow paths in end-to-end arrangements by one or more pusher devices or other source(s) of motive force as discussed herein. At block <NUM>, heated air may be supplied to the interior of the second chamber. At block <NUM>, the heated air may be recirculated across the first and second portions of the flow paths. The heated air may dry the lumber as the lumber charges progress through the second chamber.

In some embodiments, lumber charges may be organized into batches according to characteristics that affect drying time (e.g., dimensions, species, end use, starting moisture content, desired moisture content, desired drying speed, etc.). The charges of a particular batch may be fed sequentially into the kiln before feeding the charges of the next batch into the kiln. This may allow lumber charges to be fed into the kiln and moved along the flow paths at a substantially constant rate. Alternatively, in kilns with one flow path that passes through first chamber <NUM> and another path that does not pass through first chamber <NUM> (see e.g., <FIG>, <FIG>, <FIG>, and <FIG>), charges may be allocated among the flow paths based on whether the charges require preheating.

In a specific example, a first lumber charge is fed into the kiln through first charge entry portal 112a along first flow path <NUM> while a second lumber charge is simultaneously fed into the kiln through second charge entry portal 112b along second flow path <NUM>. Additional lumber charges are fed into the kiln in the same or similar manner, and at the same or similar rate, such that the lumber charges are arranged in tandem series along each flow path. This may allow the charge portals along both flow paths to be operated (e.g., opened and closed) synchronously.

In addition to the discussion of various embodiments above, figures and additional discussion are presented herein to further describe certain aspects and various embodiments of the present invention. It is to be understood, however, that a wide variety of alternate and/or equivalent embodiments or implementations calculated to achieve the same purposes may be substituted for the embodiments shown and described without departing from the scope of the present invention. Those with skill in the art will readily appreciate that embodiments in accordance with the present invention may be implemented in a very wide variety of ways. This application is intended to cover any adaptations or variations of the embodiments discussed herein.

Claim 1:
A lumber drying system comprising:
an elongated enclosure having first and second opposite ends connected by side walls and an upper wall, a pair of charge entry portals (112a, 112b) at the first end, and a pair of charge exit portals (114a, 114b) at the second end, the elongated enclosure defining a first chamber (<NUM>) and a second chamber (<NUM>) and a longitudinal axis (<NUM>) that extends through the ends and the chambers (<NUM>, <NUM>);
at least a first and a second guide member (<NUM>) that extend through the chambers (<NUM>, <NUM>) from the charge entry portals (112a, 112b) to the charge exit portals (114a, 114b), wherein the first and second guide members define substantially parallel first and second flow paths (<NUM>, <NUM>), respectively, on opposite sides of the longitudinal axis;
a heater (<NUM>) operatively coupled with the second chamber (<NUM>); and
one or more transport devices (<NUM>) operable to advance a first and a second lumber charge along the first and second flow paths, respectively, in a first direction, on respective movable supports (<NUM>),
wherein the chambers (<NUM>, <NUM>) include one or more fans (<NUM>) positioned to circulate air across the flow paths (<NUM>, <NUM>), and at least one of the chambers (<NUM>, <NUM>) includes a heating member that is selectively controllable to maintain a desired temperature within said chamber or a desired temperature differential between the chambers (<NUM>, <NUM>).