Patent Application
20120305137
1. Technical Field
The present disclosure generally relates to debarker systems, and more specifically to mechanical ring debarkers.
2. Description of the Related Art
Rotary log debarkers, commonly referred to as ring debarkers, are used to remove bark to process logs into lumber and other wood products. Rotary log debarkers often have an array of swing arms pivotally mounted to a rotatable ring. Each of the swing arms has a knife. As a log moves towards an opening of the ring, the advancing log contacts and pushes against the swing arms carried by the rotating ring. The log drives the swing arms outwardly until the knives engage the periphery of the log. The knives are urged against the log to scrape off bark.
Rotary log debarkers are typically either air-seal debarkers in which fluid pressure is maintained between the ring and an external fluid source during debarking or air-cell debarkers which are fluidically isolated from an external fluid source during debarking. Air-seal debarkers often have external fluid sources in the form of air compressors capable of delivering pressurized air to air actuators carried in a ring. The air actuators are connected to the swing arms processing the logs. The force exerted by the knives on logs can be changed on the fly by adjusting the air pressure in the actuators. For the air seal ring to operate properly, fluid communication has to be maintained between the external air compressor and the actuators. Components at the interface of the rotating and stationary parts of the ring are susceptible to failure where there is a lack of proper lubrication. Such a failure can be expensive and can result in significant machine down time. For example, significant amounts of frictional heat can be generated between seal components sliding along one another. This heat can lead to seal damage (e.g., degradation at the interface of seal components), unwanted leaking of air, and ultimately failure of seal components.
Air-cell debarkers often have rotatable rings with lightweight air bags for actuating swing arms. Air-cell rings have no air seal components so they can be rotated at relatively high rotational speeds. Each air bag is connected to a lever arm installed on a pivoting shaft carrying a swing arm. When a log enters the debarker, an end of the log strikes and moves the swing arms outwardly. The bags are compressed as the swing arms rotate. The compressed air bags exert a force to actuate the swing arms inwardly even though the air bags are not in fluid communication with an external fluid source. Air-cell rings often provide nonlinear debarking forces versus displacement, thereby providing a force gradient suitable for removing different amounts of bark from logs of different sizes, since bark thickness is often related to log diameters. Unfortunately, conventional air-cell rings are not adjustable so as to provide different force gradients. Thus, air-cell debarkers often properly debark logs having a particular diameter but improperly debark logs of other sizes because a single force gradient may not be suitable to process logs with significantly different diameters.
At least some disclosed embodiments are directed to debarker systems that can be conveniently adjusted to provide different debarking force gradients to process logs, including both large and small diameter logs. A debarker system can include an air-cell ring with swing arm assemblies actuated by force gradient adjustment mechanisms configurable to provide the different force gradients.
At least some embodiments are directed to a debarker capable of providing different force gradients for debarking logs of different sizes. Inflatable actuation devices are configured to actuate swing arm assemblies and are fluidically coupled to corresponding adjustable volume reservoir devices within a ring. The actuation devices and adjustable volume reservoir devices can be selectively isolated from an external source of pressurized fluid used to periodically pressurize the activation devices. The force, which is applied by the swing arm assemblies to different diameters of logs, is controlled by adjusting the volumes of the reservoir devices.
The debarker, in some embodiments, can be adjusted to minimize, limit, or substantially eliminate under-debarking (e.g., unwanted bark left on the logs), over-debarking (e.g., an excessive usable fiber removed with the bark), inconsistent debarking (e.g., varying applied pressures for logs having the same diameter), or the like. An initial pressure in the inflatable actuation devices can be set using an external fluid source. Small diameter logs can be processed. The pressure in the actuation devices can be adjusted (e.g., using the fluid source) until the small diameter logs are properly debarked. Larger diameter logs can be debarked. If the larger logs are under-debarked or over-debarked, pressure in the actuation devices can be decreased or increased using the adjustable volume reservoir devices. This adjusts the pressure applied by the swing arm assemblies to the large logs and allows fine tuning. Any size log between the small and large logs can be processed with a force that is generally proportional to the established force gradient, thus ensuring proper debarking. This process can be repeated to process different species of logs.
In some embodiments, a debarking apparatus includes a swing arm assembly and an air-cell ring carrying the swing arm assembly. The air-cell ring defines an opening for receiving a log and includes a force gradient adjustment mechanism coupled to the swing arm assembly. The force gradient adjustment mechanism includes a biasing device configured to be compressed as the swing arm assembly moves away from a closed position towards an open position. A force setting reservoir device is fluidically coupled to the biasing device. The force setting reservoir device is reconfigurable to change a debarking force gradient. The debarking force gradient corresponds to forces applied by a debarking tool to logs having different diameters while the biasing device and the force setting reservoir device cooperate to urge the debarking tool against the logs.
In yet further embodiments, a debarking apparatus includes a swing arm assembly having a debarking tool. A ring carries the swing arm assembly. The ring has one or more means for adjusting a force gradient of the forces applied by the swing arm assemblies to logs. The means for adjusting force gradients can include at least one biasing device and at least one force setting reservoir device. The force setting reservoir device can be an air bag, air cylinder, or the like.
A debarking apparatus, in some embodiments, comprises a swing arm assembly including a debarking tool and a ring to which the swing arm assembly is rotatably coupled. The ring includes a force gradient adjustment mechanism configured to alter forces applied by the debarking tool to logs having different diameters. In certain embodiments, the force gradient adjustment mechanism is reconfigurable to provide different force gradients. The difference between the first force gradient and the second force gradient can be at least about 10%, 20%, or 30% for different log dimensions (e.g., diameter). This allows processing flexibility. In certain embodiments, a debarking force gradient can be equal to or greater than about 38% or equal to or smaller than about 10%. The force gradient can be based on the debarking force for debarking a small diameter log and a maximum force being exerted on logs.
Some methods include pressurizing actuation mechanisms in a debarker ring. The actuation mechanisms operate swing arm assemblies to debark logs (e.g., small logs with diameters of about 5 inches). The pressure in the actuation mechanisms can be increased or decreased until desired processing is achieved. Larger diameter logs are then debarked. Reservoir devices are used to adjust a force gradient provided by the swing arm assemblies to achieve the desired processing of the larger logs. Intermediate sized logs are processed using the resulting force gradient.
The present detailed description is generally directed towards adjustable debarkers. Many specific details of certain exemplary embodiments are set forth in the following description to provide a thorough understanding of such embodiments. One skilled in the art, however, will understand that the disclosed embodiments may be practiced without one or more of the details described in the following description. The debarker components, such as rings and actuation mechanisms, are disclosed in the context of air-cell debarkers because they have particular utility in this context. However, the rings, actuation mechanisms, and other features can be used in other contexts. For example, the actuation mechanisms can be used to move other types of arms or other rotatable components that may or may not process logs, lumber, or the like.
A log can be transported lengthwise along a processing line 131 of
Referring to
A lever mechanism 160a is coupled to a shaft 162a carrying the swing arm assembly 110a. Rotation of the swing arm assembly 110a away from the closed position, as indicated by an arrow 161 of
The adjustment mechanism 144a can provide nonlinear restoring forces. The pressure applied by the debarking tool 113a to small diameter logs can be less than the pressure applied to large diameter logs. A force gradient can be adjusted to ensure proper processing of logs with significantly different diameters. If larger logs are not processed properly (e.g., too much bark or too little bark is removed), the reservoir device 152a can be used to alter the force gradient. By way of example, the reservoir devices 152a, 152b shown in
The illustrated biasing device 150a is an inflatable bag with two members 192a, 194a in fluid communication with each other. The members 192a, 194a can move relative to one another to accommodate displacement and rotation of a lever head 196a. An inflatable bag can include, without limitation, a flexible bag with one or more chambers, a bellows air bag, or the like, and can be made, in whole or in part, of one or more polymers (e.g., silicon, rubber, or the like), fabric, metal, or combinations thereof, and can provide restoring forces that vary linearly or nonlinearly with displacement. In nonlinear embodiments, the characteristics of the inflatable bag can be selected to achieve desired forces that vary with displacement. Additionally or alternatively, biasing devices can include, without limitation, hydraulic components, energy absorbers, pneumatic springs, air cylinders, or the like. For example, a biasing device can include a combination of different types of inflatable bags or can include an air cylinder.
Referring to
Throughout the day, a user can move the plate 197a any number of times. The rod 199a can have indicia (e.g., lines, markers, or the like) that can be used to accurately position the plate 197a. For example, a user can move the plate 197a using indicia on the rod 199a to locate the plate 197a at a known position suitable for processing a particular type of log. To process another type of log, the user can move the plate 197a to another position using the indicia.
Referring again to
At 310, the debarking tool exerts a pressure of about 150 lbf/inch on logs having diameters of about 5 inches. For logs having diameters equal to or larger than about 5 inches and equal to or smaller than about 25 inches, the debarking pressure slightly increases with increasing log diameters from 310 to 312. At 312, a maximum debarking pressure of about 175 lbf/inch is applied by the debarking tool. A force gradient of about 17% between 310 and 312 is greater than typical non-adjustable force gradients of about 10% of conventional debarkers. For logs with diameters larger than 25 inches, the debarking pressure gradually decreases with increasing log diameters. At 314, logs having diameters of about 38 inches are processed using a debarking pressure of about 158 lbf/inch. The vertical dashed line can correspond to the maximum log diameter to be processed.
A maximum debarking pressure at 316 of curve 302 is applied to logs having a diameter of about 26 inches to about 27 inches. At 316, the debarking pressure is about 270 lbf/inch, resulting in a force gradient of about 20%. A maximum debarking pressure at 318 of curve 304 is applied to logs having diameters of about 26 inches to about 28 inches. At 318, the debarking pressure is about 365 lbf/inch, resulting in a force gradient of about 21%. The debarker apparatus 100 can be adjusted to provide a desired force curve (e.g., curve 300, 302, or 304) selected based on, for example, the species of logs to be processed, condition of the logs, or other processing criteria.
Curves 320, 322, 324 of
The maximum pressure at 330 of curve 320 corresponds to logs having diameters of about 33 inches to about 35 inches. For logs having diameters equal to or larger than about 5 inches and equal to or smaller than about 33 inches to about 35 inches, the debarking pressure slightly increases with increasing log diameters from 332 to 330. At 330, a maximum debarking pressure of about 205 lbf/inch is applied by the debarking tool. There is a force gradient of about 37% between 331 and 330. Thus, moving the plate 197 about six inches causes more than 2 times increase in force gradient for the same initial pressurization of 50 psi. For logs with diameters larger than 25 inches, the debarking pressure gradually decreases with increasing log diameters. At 340, logs having diameters of about 38 inches are processed using a debarking pressure of about 203 lbf/inch.
A maximum debarking pressure about 310 lbf/inch at 350 of curve 322 is applied to logs having a diameter of about 33 inches to about 35 inches. At 352, the debarking pressure is about 225 lbf/inch, resulting in a force gradient of about 38%. This is almost twice as much as the force gradient of curve 302 of
The holding capacities of the force setting reservoir devices can be selectively increased or decreased to obtain the desired characteristics (e.g., force gradient, maximum tip pressure, minimum tip pressure, or the like).
To debark logs, a desired initial pressure in the adjustment mechanisms 144 can be set. Logs are then processed. The pressure levels can be adjusted until the desired amount of bark is removed. If different sized logs are under-debarked or over-debarked, pressure in the adjustment mechanisms 144 can be decreased or increased using the reservoir devices 152. This allows fine tuning of performance. One setup routine includes determining settings to debark small diameter logs (e.g., logs having diameters of about 5 inches to 10 inches). The debarker apparatus 100 is adjusted until the logs are properly debarked. Larger logs (e.g., logs with diameters greater than about 25 inches) are then debarked. The reservoir devices 152 are used to adjust the debarking pressures until the large logs are properly debarked. Thus, the initial pressure and the reservoir devices 150 are used to achieve a desired force gradient. Any size log between the small and large logs are processed with a force that is proportional to the established gradient, thus ensuring proper debarking.
Different types of force setting reservoir devices can be utilized. The reservoir device 152a discussed in connection with
It should be noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
Various methods and techniques described above provide a number of ways to carry out the invention. Of course, it is to be understood that not necessarily all objectives or advantages described may be achieved in accordance with any particular embodiment described herein. Thus, for example, those skilled in the art will recognize that the methods may be performed in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objectives or advantages as may be taught or suggested herein.
Furthermore, the skilled artisan will recognize the interchangeability of various features from different embodiments disclosed herein. Similarly, the various features and acts discussed above, as well as other known equivalents for each such feature or act, can be mixed and matched by one of ordinary skill in this art to perform methods in accordance with principles described herein. Additionally, the methods which are described and illustrated herein are not limited to the exact sequence of acts described, nor are they necessarily limited to the practice of all of the acts set forth. Other sequences of events or acts, or less than all of the events, or simultaneous occurrence of the events, may be utilized in practicing the embodiments of the invention.
Although the invention has been disclosed in the context of certain embodiments and examples, it will be understood by those skilled in the art that the invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses and obvious modifications and equivalents thereof. Accordingly, it is not intended that the invention be limited, except as by the appended claims.
