End-dogging head saw and method

Information

  • Patent Grant
  • 6817393
  • Patent Number
    6,817,393
  • Date Filed
    Friday, July 12, 2002
    21 years ago
  • Date Issued
    Tuesday, November 16, 2004
    19 years ago
Abstract
An end-dogging head saw is disclosed comprising a log cradle for supporting a log, a log-turning device for rotating the log into proper alignment with a pair of band saws, the log-turning device depending from overhead log carriages which move the log into contact with the band saws, and a carriage drive for powering the overhead log carriages, whereby short logs can be quickly and efficiently processed. The invention also seeks to provide a method for using the apparatus, comprising rotation of a log through 360 degrees to allow for cutting at any desired angle along the length of the log. The method allows for maximal recovery of high-quality lumber.
Description




FIELD OF INVENTION




This invention relates to sawmills, and particularly to sawmills adapted to recover lumber products from short logs.




Standard sawmills are often unable to recover good quality lumber from short logs, i.e. 8 feet and under, resulting in waste of potential lumber material as wood chips. While some innovative sawmills have attempted to address this need, the present invention provides a novel means of recovering a maximal amount of high-quality lumber from logs under 8 feet.




The development of the present invention was necessitated by the limitations of the standard sawmills in the industry in addressing short log lumber recovery. In particular, some means are required for recovering lumber products with a minimal amount of waste chip production.




In response to this problem, the present invention seeks to provide an apparatus and process for maximizing high-quality lumber recovery while limiting the amount of waste wood chips. In order to accomplish this, the present invention comprises a novel positioning and cutting apparatus which, when employed in the manner set out below, will allow lumber processing companies to maximize yield from short logs of previously little recoverable value. A log is positioned in a log cradle, stabilized by means of end dogs, and passed through band saw cutting means by means of overhead log carriages, but the log can be returned to its initial pre-cutting location any number of times and rotated through a full 360 degrees by a log-turning device to any desired position before again passing the log through the cutting means. Scanning means are employed to determine log diameter to enable cradle adjustment and initial log positioning.




While the standard sawmills usually cannot economically recover lumber from logs less than 8 feet in length, the present invention can quickly and efficiently process such logs into boards ranging from 2 inches×½ inch×1 foot to 10 inches×10 inches×8 feet. In addition, the present invention is compact in size and can be used either in concert with existing sawmills or as a stand-alone unit for small-log operations. Also, the fully rotatable positioning mechanism allows for tangential cuts at any face rather than the usual four faces possible in standard sawmills, enabling maximal yield. Another feature of this invention is the use of band saws rather than the standard circular saws, which allows for cutting of logs up to 28 inches in diameter.




DESCRIPTION OF THE BACKGROUND ART




Prior attempts to provide small log recovery sawmills include U.S. Pat. No. 4,117,755, wherein is disclosed a log sawing and transport system that positions a log, uses end dogs to secure it, and moves the log through cutting means with axially moveable carriage units. However, this apparatus fails to maximize high-quality lumber recovery, as it employs circular saws to produce sector-shaped pieces. At least one of the saws can be adjusted to different angles, but this is addressed to the specific problem of quarter-sawing rather than recovery of high-quality boards.




Other prior art has addressed related problems. U.S. Pat. No. 3,459,246 discloses a lumber plant that employs band saws adjustable to the diameter of a given log, using scanning means to determine the diameter. Also, logs are gripped at their ends to be transported through paired cutting means. However, this invention fails to consider problems of yield maximization of short logs, as it primarily addresses band saw adjustment.




Canadian Patent No. 1,108,968 discloses a scrag saw mill dogging system that employs dogs on moveable carriages. However, the dogs attach to the log's sides, the carriages are not utilized during the actual cutting phase, and the invention is directed specifically to a problem associated with scrag saw mill operation.




Multiple passes through cutting means (e.g. U.S. Pat. No. 5,503,202) and rotatable dogging means (e.g. U.S. Pat. No. 5,421,385) are known in the art, but they are not directed towards short log lumber recovery maximization as in the present invention.




The present invention offers a novel solution to the problem of efficient and cost-effective small log lumber recovery. The innovative use of an adjustable log cradle, rotating end dogs, movable carriages, adjustable band saws, and other features addresses a serious lumber industry waste issue.




SUMMARY OF THE INVENTION




The principal object of this invention is, therefore, to seek to provide a lumber-processing apparatus and method adapted to the specific problem of short log recovery, the apparatus comprising means for rotating, transporting, and cutting short logs. The method uses the disclosed apparatus to make particular cuts of a short log.




Other objects will appear from the description and the drawings.




Accordingly, the present invention provides an end-dogging head saw comprising a log cradle for supporting a log, a log-turning device for rotating the log into proper alignment with a pair of band saws, the log-turning device depending from overhead log carriages which move the log into contact with the band saws, and a carriage drive for powering the overhead log carriages, whereby short logs can be quickly and efficiently processed. The invention also seeks to provide a method for using the apparatus, comprising rotation of a log through 360 degrees to allow for cutting at any desired angle along the length of the log. The method allows for maximal recovery of high-quality lumber.











BRIEF DESCRIPTION OF THE DRAWINGS




In the drawings, according to a preferred embodiment of the invention:





FIG. 1

is a diagrammatic perspective view of the present invention attached to log-feeding and board-removal mechanisms;





FIG. 2

is a detailed side view of the present invention;





FIG. 3

is a detailed end view of the present invention;





FIG. 4

is a cross-sectional view of a log displaying the positions of the various cuts to be made using the present invention;





FIG. 5

is an end view of a band saw;





FIGS. 6 and 7

are end views of the log cradle provided with servo motors;





FIG. 8

is a side view of the log cradle provided with servo motors;





FIG. 9

is a schematic of the electrical system;





FIG. 10

is a diagrammatic perspective view;





FIG. 11

is a perspective view of a modified cradle; and





FIG. 12

is an end view of the modified cradle.











DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT




Referring now in detail to the Figures, and particularly

FIGS. 1

to


3


, an end-dogging head saw is a preferred embodiment of the present invention and is generally denoted as


10


. The end-dogging head saw


10


is comprised of a log cradle


15


, a log-turning device


25


, band saws


30


, and overhead log carriages


35


on a frame


34


. As illustrated in

FIG. 1

, the end-dogging head saw


10


is fed with logs


20


by means of a log-feeding mechanism


11


, driven by a hydraulic cylinder


12


, and the processed lumber passes out of the end-dogging head saw


10


by means of parallel or perpendicular board-removal mechanism


13


.




The log cradle


15


is adjustable either automatically or manually, and it receives the log


20


for the initial positioning stage (see

FIGS. 6

,


7


, and


8


). The log cradle


15


tilts from side to side and is capable of vertical movement, through use of hydraulic cylinders


50


or servo motors


51


and chain


52


, allowing the operator to position the log


20


in proper alignment for cutting. A scanner


18


(shown in

FIG. 9

) detects the diameter at each end of log


20


and this data is sent to PLC input/output port


19


(shown in

FIG. 9

) for processing by the PLC


17


to enable automatic position adjustment of the log cradle


15


, or manual adjustment from an operator console


200


(shown in FIG.


9


).




A PLC, or programmable logic control, is a special purpose computer aimed at implementing control systems. The PLC


17


used in the present invention has a series of inputs and outputs to control the functionalities of the end-dogging head saw


10


. PLCs are modular in nature such that each function is a separate module. Modules may be readily added to the design in order to customize the system for a particular use. The number of modules implemented in a PLC will vary but each module will have the same basic function of obtaining or delivering controls and information between the measurement level and the operator interface level. The program code is an integral part of the PLC. The program code is usually developed and edited on a programming computer and then stored on the PLC. The program code for the end-dogging head saw


10


was also developed in modules, wherein each module incorporates the various measurements taken, the operator interface, and the control functions required.





FIG. 9

illustrates a schematic block diagram of the PLC input/output ports


19


. The inputs are read in along various input ports on the PLC


17


. The operator console


200


may have several inputs, such as switches or sensors, to dictate when the end-dogger head saw


10


is to start up. The operator console


200


has an input for powering up the system, starting the saw motors


45


, and utilizing the end dogs


65


and


70


. The operator may choose either to control the end dogs


65


and


70


manually or allow certain PLC modules to perform those functionalities. The operator interface


202


has various PLC input/output ports


19


to read in saw tension, saw position, thickness selection, angular log position, log dimensions, and alarms. The operator inputs his selections at the operator interface


202


which is then read in by the PLC


17


. The saw tension feedback


121


from strain gauge


120


is a measurement taken at the PLC input to ensure that the level of tension is within an acceptable range. The log position is scanned by scanning means


21


and a position value is read in by the PLC


17


. The output from the limit sensors


204


is read in by the PLC


17


to measure the position of the overhead log carriages


35


in relation to the position of the log


20


. The log end diameter is scanned by scanning means


18


similar to those used for the log position. The PLC


17


requires the log end diameter to calculate the position for the band saws


30


. The bed position encoders


16


measure the position of the log cradle


15


as values are read in at the PLC


17


input. Various other inputs may be added for further control of the end-dogging head saw


10


. These other inputs are shown in

FIG. 9

as extras.




The PLC


17


utilizes all measurements taken at the inputs in various modules of the PLC program. The PLC


17


then outputs various control information to various devices. The PLC


17


will output a signal to the saw motor's positioning system


75


dictating whether the band saw


30


should move in or out. The carriage motor


85


is connected to a PLC output and awaits a signal dictating the feed speed. The carriage motor


85


may also be manually controlled by a set of manual inputs used by the operator. The hydraulic cylinder


95


is controlled by a dog input/output signal sent by the PLC


17


. The log rotation motor


55


, saw position drive


75


, and log position signals are sent by the PLC


17


on a continuous or interleaved basis depending on the control feedback required by the system. If the operator console


200


manually adjusts these positions and speeds then these signals may be unnecessary. The log transfer signal activates the log feeding mechanism


11


. Output signals to various pilot lights allow the operator to monitor the functionality of various parts from a distance. The alarm signals are important to the end-dogging head saw


10


. Various PLC alarm modules may be continuously running in the background as they check whether various measurements are in an acceptable range or are surpassing a particular threshold.




The log-turning device


25


is comprised of a drive dog


65


, powered by an electric servomotor


55


with built-in brakes


60


, which grips the log


20


and rotates it either clockwise or counter-clockwise. A free dog


70


grips the opposite end of the log


20


, the two rotating dogs


65


and


70


maintaining the log


20


in a stable position properly aligned for cutting. Means can be employed to allow the log-turning device


25


to “remember” earlier positions of the log


20


for cuts on the same plane.




Paired band saws


30


are employed as the cutting means in this preferred embodiment of the present invention. They are fitted with independent electric motors


45


as well as tensioning means (not shown) such as are common in the art. The band saws


30


, having endless blades


31


, are also fitted with independent electric servo motor positioning systems


75


and chain drives


76


to control axial displacement as necessary, depending on the diameter of the log


20


.




The end-dogging head saw


10


is fitted with two overhead log carriages


35


which hold the log


20


in a generally horizontal position for contact with the band saws


30


. The overhead log carriages


35


are driven by a carriage drive


40


, which is comprised of a cable


80


linked to a forward/reverse electric or hydraulic variable speed motor


85


. A hydraulic cylinder


95


is positioned between the overhead log carriages


35


to force the end dogs


65


and


70


into the ends of the log


20


, and the cable


80


is fed through two drums


90


to maintain a controlled, steady speed for movement in both directions.




The operator console


200


allows the operator of the present invention to perform the following method either manually, automatically, or a combination of both, controlling the feed and dogging of log


20


, the positioning of band saws


30


, and the cutting of the log


20


by movement between the band saws


30


. A manual override is available on the operator console


200


for all potentially automatic functions.




To maintain proper tension in the saw blades


31


and provide more even cuts, a strain gauge


120


(see

FIG. 5

) is provided to monitor movement of upper and lower band saw wheels


122


and


124


and provide signals to control the speed of the motor


85


and the carriage


35


.




In

FIGS. 10 and 11

a modified end-dogging head saw generally denoted as


101


has a log cradle


64


. The band saws


30


overhead log carriages


35


the same as those illustrated in FIG.


1


. The end-dogging head saw


101


is fed with logs


20


by means of a log feeding conveyor


41


and the processed lumber


21


passes out of the end-dogging head saw


101


by means of parallel and transverse board removal mechanisms


13


and


14


respectively where board removal mechanism


14


has three transverse board conveyor belts


14




a


,


14




b


, and


14




c


. The log cradle


64


receives an end of the log


20


.




A centering device


53


on the log cradle


64


includes a pair of clamping blades


46


and


47


similar to the indentation of the cradle


15


V-shaped indentations in mating a second pair of clamping of blades


48


,


49


and


49




a


on the cradle


64


is spaced from the clamping blades


46


and


47


and have identical V-shaped indentations.




Inward and outward movement of the blade


46


and


47


is provided by a worm drive


42


and a worm drive


43


moves the blades


48


and


49


in a similar manner to grip and center the log


20


. The log cradle


64


is also used to move the log


20


longitudinally. The blades


46


and


47


have side guides


36


,


37


so that the pair of blades can be moved by a chain drive


38


and motor


39


toward the conveyor


41


to grip a log


20


and pull the log into the cradle


64


.




If the log


20


is less than about


2


feet in length the log can be held by the blades


46


and


47


without being engaged by the blades


48


,


49


and


49




a


. The log cradle


64


is operated automatically or manually and receives the forward end of the log


20


as shown in

FIG. 10

as the blades


46


and


47


move toward the blades


48


,


49


and


49




a.






The blades


46


and


47


are positioned on the log


20


and activated to grip the log


20


and pull the log into the cradle


64


. The two sets of blades


46


,


47


and blades


48


,


49


,


49




a


are then moved by their worm drives


42


and


43


respectively to center the log


20


.




The log is now centered in the horizontal plane and is ready for lifting. A sensor mounted on each centering mechanism is used for measuring the log diameter. The numbers are stored in memory. The cradle


64


moves upward in position for dogging. If the log needs to be centered differently, a +/−6 in. adjustment is possible in every direction. The operator has to switch to manual mode to do so using hydraulic cylinders


55




a


(see FIG.


11


). The log length and diameters stored in memory are used to determine the current patterns and to provide the lumber volume.




The cradle


64


can also be raised and lowered (as shown in

FIG. 12

) by activating hydraulic cylinder


55


and


56


on the frame


36


of the saw


10


to move cables


57


and


58


respectively on the under side of the cradle


64


. The cables


57


and


58


have their outer ends attached to the frame


34


. The cables


57


and


58


entrain suitable pulleys


59


.




As shown in

FIG. 9

the PLC


17


is adapted for use with the log cradle


64


of

FIGS. 10

,


11


and


12


.




The PLC includes controls (shown in broken lines on

FIG. 9

) for transverse movement of blades


46


and


47


, through worm drive


42


, transverse movement of blade


48


,


49


and


49




a


, by means of worm drive


43


, and longitudinal movement of blades


48


and


49


by activating the hydraulic motor


39


. Raising and lowering cradle


64


to position a log


20


between dogs


65


and


70


is done by activating hydraulic cylinders


55


and


56


.




As shown in

FIGS. 10 and 12

, loading a second log


20


on the carriage


64


takes place while a log


20


is being sawed.




Referring to all of the Figures, the utility of the present invention becomes clear in the following method of use. The operator of the end-dogging head saw


10


uses the operator console


200


to feed a log


20


by means of log-feeding mechanism


11


(powered by hydraulic cylinder


12


), the log


20


resting in the log cradle


15


. The log cradle


15


is then adjusted, based on data from the scanning device


21


and PLC processor


19


, using the hydraulic cylinders


50


or servo motors


51


to ensure proper alignment of the log


20


relative to the band saws


30


. The log-turning device


25


then engages the ends of the log


20


, gripping the ends by means of end dogs


65


and


70


. The log cradle


15


then moves down to allow progress of the log


20


into the cutting stage. The operator then uses the log-turning device


25


, via the drive dog


65


, to rotate the log


20


into the desired position, the electric servomotors


55


and brakes


60


affording necessary control. The operator then adjusts the band saws


30


using the positioning systems


75


, and the band saws


30


are powered by electric motors


45


. The log


20


is carried through the cutting area of the band saws


30


by means of the overhead log carriages


35


, which are powered by the carriage drive


40


. The band saw blades


31


are preferably of a thickness of 0.035 inches to 0.042 inches and a width of 1¼ inches to 2 inches, set preferably on 19-inch or 20-inch wheels.




After the log


20


is driven through the band saws


30


, the overhead log carriages


35


return the log


20


to its original pre-cutting location. During the return, the log


20


can either be (a) rotated by means of the log-turning device


25


into a different desired position or (b) not rotated and the band saws


30


can be adjusted to make a deeper cut.




As illustrated in

FIG. 4

, a sawing pattern can be employed to maximize production of high-quality boards


100


. By making a plurality of tangential cuts at various angles through rotation of the log


20


, a small core will remain. A beam


105


can be cut from this core, either 4 inches×4 inches, 5 inches×5 inches, or 6 inches×6 inches, depending on the core diameter, with the small amount of remainder as waste


110


for wood chips. The beam


105


is automatically produced and is released to the board-removal mechanism


13


, as are the boards


100


that are produced during this process, the board-removal mechanism


13


preferably comprising a conveyor belt


14


and transverse conveyor belts


14




a


,


14




b


and


14




c


. The PLC


17


can be programmed to cut boards to custom dimensions to suit customer requirements.




It will be clear to any person skilled in the art that modifications of and adjustments to this invention, not shown, are possible without departing from the spirit of the invention as demonstrated through this preferred embodiment.



Claims
  • 1. An end-dogging head saw apparatus for processing without discarding logs having different lengths, comprising in combination:a frame; a log cradle, operatively coupled to the frame, for supporting a log; at least one band saw, operatively coupled to the frame, for cutting the log; overhead log carriages, operatively coupled to the frame, for receiving the log from the log cradle; a log-turning device, depending from the overhead log carriages constructed and arranged to rotate the log into proper alignment for cutting of the log at an angle with the at least one band saw; a carriage drive, operatively coupled to the overhead log carriages, for powering the overhead log carriages; and the overhead logs carriages, constructed and arranged to receive the log, each having means for moving independently to respective positions that accommodate the length of the log and for moving the log into contact with the at least one band saw; whereby logs of different length can be quickly and efficiently processed by the apparatus.
  • 2. An end-dogging head saw apparatus as in claim 1, further comprising automatic means, operatively coupled to the end-dogging head saw, for adjusting the log cradle.
  • 3. An end-dogging bead saw apparatus as in claim 2, wherein the automatic means for adjusting the log cradle comprise hydraulic cylinders.
  • 4. An end-dogging head saw apparatus as in claim 1, further comprising a scanner, operatively coupled to the end-dogging head saw, for detecting the log diameter and a processor for utilizing the data received from the scanner, enabling efficient cutting.
  • 5. An end-dogging head saw apparatus as in claim 1, further comprising an electric servomotor and brakes operatively coupled to the log-turning device.
  • 6. An end-dogging head saw apparatus as in claim 1, wherein the log-turning device further comprises means for returning the log to its original position before contact with the at least one band saw to allow for further cutting.
  • 7. An end-dogging head saw apparatus as in claim 1, wherein the log-turning device further comprises dogs for stabilizing the log position, one dog driven by the log-turning device and the other rotating freely, allowing for stable rotation of the log by the log-turning device.
  • 8. An end-dogging head saw apparatus as in claim 3, further comprising manual override means, operatively coupled to the end-dogging head saw—for automatic functions provided by the automatic means.
  • 9. An end-dogging head saw apparatus as in claim 1, further comprising a further band saw and means for movement of the at least one band saw toward and apart from the further band saw, wherein movement means are operatively coupled to the end-dogging head saw.
  • 10. An end-dogging head saw apparatus as in claim 9, further comprising independent electric servo positioning systems, operatively coupled to the end-dogging head saw, to maintain an axial displacement of the at least one saw.
  • 11. An end-dogging head saw apparatus as in claim 10, where the pair of band saws includes two wheels to house a cutting blade, further including a strain gauge situated between the two wheels of the at least one band saw for controlling speed of the overhead log carriages.
  • 12. An end-dogging head saw apparatus as in claim 1, wherein the carriage drive includes a cable operatively coupled to the carriage drive, and an electric or hydraulic variable speed motor, operatively linked to the cable.
  • 13. An end-dogging head saw apparatus as in claim 12, further including cable drums, operatively coupled to the cable, to maintain accurate and steady speed of cable movement.
  • 14. An end-dogging head saw apparatus as in claim 1, further comprising a hydraulic cylinder operatively coupled between the overhead log carriages to force the dogs into the log.
  • 15. An end-dogging head saw apparatus as in claim 1, wherein the at least one band saw is powered by independent electric motors operatively coupled thereto.
  • 16. A pre-positioning device for use with a head saw apparatus with end-dogging means to grip the log from the pre-positioning device, comprising:a cradle for moving a log into position for dogging by the head saw apparatus; a set of clamping blades for gripping the log, where the set includes a pair of blades disposed substantially in parallel and an opposing third blade, the pair of blades and the third being operatively mounted at opposing ends of the cradle, and where each of the pair of blades and the third blade being constructed and arranged to engage the log at a first position and a second position along the log so as to securely grip the log for movement toward the head saw apparatus; drive means, being operatively coupled to the set of clamping blades and mounted onto the cradle, for moving the set of clamping blades inwardly and outwardly to engage the log; and at least one sensor, operatively coupled to the cradle, for sensing at least one physical characteristic of the log, the at least one sensor having means for processing at least one physical characteristic measured by scanning the log to enable proper positioning of the log prior to dogging by the head saw apparatus.
  • 17. The pre-positioning device of claim 16, further includes a second cradle and at least one set of clamping blades, operatively mounted onto the second cradle, for engaging the log at a third position along the log so as to securely grip the log for movement toward the head saw apparatus.
  • 18. The pre-positioning device of claim 16, wherein the first positions and the second position are approximately equidistant from either end of the log.
  • 19. The pre-positioning device of claim 16, wherein the moving means is at least one hydraulic cylinder operatively coupled to the carriage for raising and lowering the cradle, the at least one hydraulic cylinder is activated by the at least one sensor.
  • 20. The pre-positioning device of claim 16, wherein the drive means is a worm drive system operatively coupled to the at least one set of blades for raising and lowering the cradle, the worm drive system is activated by the at least one sensor.
  • 21. The pre-positioning device of claim 16, wherein the each blade has a V-shaped indentation.
  • 22. The pre-positioning device of claim 17, wherein the each blade has a V-shaped indentation.
  • 23. An end-dogging head saw apparatus for processing without discarding logs having lengths, comprising in combination:frame; a log cradle, operatively coupled to the frame, for supporting a log; at least one band saw, operatively coupled to the frame, for cutting the log; overhead log carriages, operatively coupled to the frame, for receiving the log from the log cradle; a log-turning device, depending from the overhead log carriages, constructed and arranged to rotate the log into proper alignment for cutting of the log at an angle with the pair of band saws, and having means for returning the log to its original position before contact with the at least one band saw to allow for further cutting; and a carriage drive, operatively coupled to the overhead log carriages, for powering the overhead log carriages; the overhead log carriages, constructed and arranged to receive the log, each having means for moving independently to respective positions that accommodate the length of the log and for moving the log into contact with the at least one band saw; whereby logs of different length can be quickly and efficiently processed by the apparatus.
  • 24. An end-dogging head saw apparatus as in claim 1, wherein the pair of band saws are constructed and arranged to tangentially cut the log at a plurality of angles through rotation of the log by the log-turning device, and the plurality of angles selected to form a sawing pattern.
  • 25. An end-dogging head saw apparatus as in claim 23, wherein the pair of band saws are constructed and arranged to tangentially cut the log at a plurality of angles through rotation of the log by the log-turning device, and the plurality of angles selected to form a sawing pattern.
Priority Claims (1)
Number Date Country Kind
2353139 Jul 2001 CA
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Number Name Date Kind
3190323 Johansson Jun 1965 A
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4069851 Bibler Jan 1978 A
4117755 Hasenwinkle et al. Oct 1978 A
4294149 Olsson Oct 1981 A
4996900 Schmidt et al. Mar 1991 A
5035166 Carlson et al. Jul 1991 A
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Foreign Referenced Citations (1)
Number Date Country
1 108 968 Sep 1981 CA