CA1066592A - Sawmill log-handling system - Google Patents

Abstract

SAWMILL LOG-HANDLING SYSTEM

Abstract of the Disclosure Logs are advanced through a saw while they are engaged between driven pusher dogs and retarded hold-back dogs. The pusher dogs are mounted on a lower endless roller chain below the logs, and the hold-back dogs are on an upper endless roller chain above the logs.
The upper chain and its hold-back dogs are vertically movable to elevations dependent on the elevation of a log, thus assuring proper engagement. When the sawed portion of a log is retained laterally on a support, the hold-back dogs are moved forwardly away from the log so that a hold-back dog will be in the path of the next log to be handled by the system.

Description

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This invention relates to sawmill apparatus and methods, and particularly to a log handling system whieh engages and advances logs accurately through a saw; even in instances where the logs are of irregular sizes and shapes.
In one prior art system, known as a skrag saw, a log is balanced on a narrow ehain carrier provided with pusher dogs `
which push the logs through circular saws or opposed band saws.
On the outfeed side of the saws, upright guides called "splitters"
are positioned in the cut made by the saw blade. The inaccura~
cies inherent/in such systems restrict their praetieal use, where ;
aceuraey is important, to the sawing of small short logs of `
essentially eylindrieal characteristics. `
It has been recognized heretofore that logs of varying lengths may be accurately sawed by engaging their oppo- -site ends by members which apply a gripping force thereto. U.S.
patents 3,503,428 and 3,731,578 to Bo Ingemar Aekerfeldt disclose `
this general coneept in highly complicated systems whieh are far more eomplex and expensive than the present invention. Aekerfeldt suspends his forward and rear log-engaging means from a eommon overhead traek; both log-engaging means are coupled to and dis-engagable from a eommon drive eable; and, a spring is used to apply a gripping foree between the log-engaging means.

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~, The present inventlon represents a signl~icant advance over the prior art systemSdescribed above. Unlike the prior skrag saws, logs of irre~ular shapes may be sawed accurately, and the necessity for the often-trouble~me splitters ;s avoided. It is superior to t.he Ackerfeldt system due to its relative simplic~ty which ma~es the app~ratus more compact, simpler to operate, les~ expensive to manufacture and sell, and thus more access~ble to the small or medium si~ed sal~nill operator.
One ob~ect o~ the invention is to hold logs under positive control during sawin~, thus providing a degree of safety and accuracy which cannot be att~ined in systems where logs are held precariously. ~-Another obJect of the invention is to provide a system capable of handling rough, mis-shapen logs which cannot be fed throu~l many existing systems due to their limb or knot projectlons, crooks9 sweep~ swell~
rotten heart~ angled or spl~ntered ends and other rl~ws.
Still another obJect of the inventi~n is to produce co~.pletely accurate products, u~ually flitches3 to -provide a maximum recovery of l~nber even from poor quality logs~
A further ob~ect o~ the invention 1~ to provide a system which may handle n random mix and sequence o~ log8 of varying lengths and diameter~.
Another obJect is to proYide a system whlCh i8 relatively uncomplicated so th~t lt may be manufactured .. . . ~.

~nd sold at moderate prlces, thu~ making it available to `~
a l~rge variety of sawmill operators.
~ nother ob~ect i5 to provide a system which i9 extremely compact and does not require an excessive amount of mill space.
Other ob~ects of the invention are to provide a :-system ~Yhich is extremely fast due to its avoid~nce o~
the necessity of troublesome components such as spl~ttera - or chipper heads; to provide a system c~pable Or handllng,;~
~0 hard wood, soft wood or frozen stoclc; and, to provide a system whicll is due to its relative simplicity and automatic features does not require an experienced ~ :
operato~.
Various ones of the preceding ob~ects of the invention are attributable to one or more of the inve~tl~e - concepts utilized in the preferred embodiment of the invention disclosed in this 3pecification. ):
One of the inventi~ve concepts relates to the use .~ ~
of a driven lcg-engagin~ means operable on the rear or ' -:
trailing end of a lo~, together with a forward log-eng~ing mèans which engages the for~Yard or leading end of a log ~- and is supported on a chaln or other endless carrler positioned above the path of the log. Another lnventlve , concept lnvol~es the use of a driven rear log-engaglng mean~
and a folward log-engaging means ~hich has its mo~ement . .i- i.

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retarded as a log is advanced throu~h a saw, whereby the log lS graspea ~uring sawing between the driven rear log-engaging means and the retarded forward log-engaging means.
Still another inventive concept pertains to the ~ arrangement which advances the forward log-engaging means away from the log after the sawed log :is held on its support by a stabilizer means. A further inv~tive concept is directed to a vertically adjustable forward log-engaging means which is moved vertically in response to signals from a sensor for detecting the elevation of the forward end of a log.
In accordance with one broad aspect, the invention relates to a sawmill log handling system for advancing logs longitudinally along a given path from an infeed side of a saw, `~
through the saw and to an outfeed side of the saw, said system comprising, rear log engaging means for engaging a rearward end of a log, rear drive means for moving said rear log engaging means along said given path to carry said logs from said infeed .
side, through the saw and to said outfeed side, forward log engaging means for engaging a forward end of said log while said - 20 log is being moved by said rear drive means, said forward log engaging-means being m~vable from the ineed side to the~out~eed side-as the log is--cut by the saw-f and means for mo~i-ng one of the log engaging means verticalLy to accommodate logs of ~` different diameters. -A typical preferred system embodying all of the -inventive concepts is disclosed in the accompanying drawings wherein: _ Fig. 1 is a perspective view, diagramatic in some-respects, of the log handling system of the inventionT ;
Fig. 2 is a side elevation of the system-of Fig. l;
Fig-. 3 i~ a plan view-of-the log handling syst~m of Fig.- l; and, ,^ _ 5 _ .:
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Fig. 4 is a sQcti~nal ~iew thereof as seen along the '~
line 4~4 in Fig. 2; and Fig. 5 is a perspective view of a modified log :~
handling system.
Throughout the drawing~" a twin bandsaw assembly is shown in diagrammatic ~orm having a pair of saw bands 2 and 4 supported on their respective wheels or pulleys 6, 8, 10 and ~:12. Means are provided for rotating the wheels in a conventional manner to cause the bandsaws to cut a ~' ~'` '' ~
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log which is advanced longitudinally therethrough, the sides of the log being cut by the adjacent vertical portions of the saw -bands 2 and 4. This normally produces two slabs and a center ~'-heart piece which is known in the art as a flitch or cant. The saws are preferably shifting saws for producing a heart piec~e of a thickness ranging from about four inches to any larger size which may be accommodated byisecondary reduction resaws available at the mill. Of course, any number of saw blades of the band or rotary type may be used within the context of this invention. -A pair of known driven jump turning rolls 14 and 16 are provided at the infeed side of the saw blades 2 and 4.
These rolls 14 and 16 are used to support and orient a log prior -- to sawing. They have spaced full length guide bars to promote engagement with a log and they are rotatable about their longi- ~ -tudinal axes by a hydraulic motor so as to position a log pre-liminarily at a desired orientation. The rolls 14 and 16 are vertically movable which permits them to be elevated to raise a log above the path of the pusher dogs described below.
As seen in Fig. 3, the log turning rolls 14 and 16 are spaced apart to accommodate therebetween an endless roller ; chain 18 which is positioned below the path followed by loys in the apparatus. This chain 18 serves as a lower carrier for supporting a series of rear log engaging means such as the pusher ~;
dogs illustrated at 20. The upper horizontal run of the chain 18 rides on a guide rail 22 and the chain is engaged on a series !~
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of sprockets 24, 26, 28 and 30, the latter being shown only in Fig. 2. The lower horizontal run of the chain extends between the pulleys 26 and 30 and the chain is moved in a continuous path on its spr~ckets and guide rail 22 by a drive means including the hydraulic fluid motor 32. The sprocket 34 of hydraulic motor 32 is engaged with the chain 18 by a reduction system illustrated in Fig. 1 and including the chain 36, enlarged sprocket 38, shaft 40, reduced sprocket 42, chain 44 and the sprocket 46 which is coupled directly to the sprocket 28 for the chain 18. Operation of the hydraulic motor 32 drives the chain 18 and its pusher dogs 20 ~in a counter-clockwise direction as ;
seen in Figs. 1 and 2, thus causing the pusher dogs 20 to engage the rear end of a log and propel the log along a given path in the direction indicated by the arrow 48. This carries the log through the saw and to the outfeed side of the saw.
Prior to movement of a log into the saw bands 2 and 4, its forward end is engaged by a hold-back dog 50 which serves as the forward log-engaging means of the apparatus. Dogs 50 -are supported on an upper roller chain 52 which is continuous and moves in an endless path on the guide rail 54 and sprockets 56 and 58. These sprockets 56 and 58 are rotatably supported on an upper frame 59-formed of a pair of elongated parallel plates 60 and 62 which are spaced apart to support the guide rail 54 as shown in Fig. 4. The upper frame 59 is vertically movable ~, ~ 7 ~
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to permit the dogs 50 to engage the upper part of the forward end of a log at an appropriate elevation. This vertical move-ment is produced by a hydraulic cylinder 6~ which has its plunger rod 66 connected at 67 to the frame 59 and to a hori-zontal leg of a bellcrank lever 68 which is pivotally mounted `~
on the rotatable stationary pivot axle 70. The vertical arm of the bellcrank lever 68 is pivotally connected to an elongated link 72, the opposite end of which is connected to the upper end of a similar leg of a bellcrank lever 74, the latter being ;
10 supported on a stationary pivot axle 76 and being connected to ~
the frame at 78, thus causing the portion of the frame in the ~ .
vicinity of the saws to move vertically the same distance as the ,:
frame in the vicinity of the hydraulic cylinder 64i. It will be observed that an identical arrangement including an hydraulic cylinder and bellcrank linkages is provided on both sides of the frame 59 which supports the chain 52 and its hold-back .
- dogs 50. ' The operation of the hydraulie eylinders 64 may be ~:
performed by a maehine operator who observes the elevation of ` ~
20 the forward end o~ a log being ~ed towara the saw by the rear ~ -pusher dogs 20. However, this ehange in elevation may be per-~ -formed automatieally by providing a limit switeh 80 at a loca-tion prior to a point where the forward end of a log comes into contact with a hold-baek dog 50. The actuator of limit switch 80 will be eontaeted by a log of large diameter, thus sensing 5"' :~

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the elevation of a forward end of a log prior to engagement of the log with the hold-back dogs 50. Actuation of the limit switch 80 will automatically operate hydraulic cylinder 64 to elevate the frame 59, thus moving the chain 52 and dogs 50 to an appropriate height. -;
During the sawing operation, firm engagement of the hold-back dogs 50 with the log is assured by retarding the move- -ment of the dogs 50 as the log is advanced through the saw by ~`
the drive means for the pusher dogs, thus causing the log to be grasped between the pusher dog 2a and the hold-back dogs 50.
The retardation of the hold-back dogs S0 is achieved by resis-tance means which includes the friction of the means for sup-~
porting and engaging the chain 52, and also the deactivated `
hydraulic fluid motor 82 which is coupled to the sprocket 58. -Actually, the motor 82 will be connected to the sprocket 58 by a ~
; reduction means similar to that used for driving the lower chain - ;
- 18 with the motor 32, but this construction has been eliminated from the drawings for purposes of clarity. Retardation of the hold-back dogs may also be produced by a brake on one of the sprocket shafts for chain 52. Initial engagement of the hold~
back dog 50 with the log may be achieved by momentarily revers~ing the motor 82. `~
The motor 82 also serves as a drive means for moving the hold-back dog 50 forwardly at or toward the conclusion of the saw operation. At this point, the log will be supported on a -.
rail 84 shown best in Fig. 4. Upon completion of sawing, the ' `

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slabs will fall onto the conventional screw rolls 86 which are provided with helical ribs (not shown) and are rotated about their axes to move the slabs in the directions indicated by the arrows 87. The flitch or cant is held or retained on the upper edge of the rail 84 by the rolls 88 and 90 which are stabilizer -means for retaining the log on the log support rail 84 to prevent lateral displacement of the logs after sawing. The rolls 88 and 90 are supported by vertical shafts 92 and 93, the upper ends of -which are pivotally mounted for lateral swinging movement.
Of course, once the log is engaged by the stabilizer ";!
rolls 88 and 90, the hold-back dogs 50 are no longer re~uired.
As these dogs 50 arrive at and engage the limit switch 94, a ~- -circuit is actuated to energize the hydraulic motor 82 for the upper chain 52. The hydraulic motor 82 drives the chain 52, moving the dogs 50 forwardly away from the log when the log is ;~
retained by the stabilizer rolls 88 and 90. The hydraulic motor 82 is deactivated when one of the hold-back dogs 50 arrives at and trips the limit switch 96 positioned at the rear ena of the upper frame 59.~ This deactivates the hydraulic motor 82, and ~ -stops movement of the upper carrier chain 52 at a point when one of the hold-back dogs 50 is positioned in the path for engaging the forward end of the next log to be moved through the apparatus.
The operation of this apparatus will be evident from the preceding description. A log is fed to the turning rolls 14 and 16 by a conventional log deck which has a log stop and loader.
The rolls 14 and 16 are rotated by an hydraulic motor (nct shown) to place the log at an appropriate orientation. The rolls 14 and 16 are elevated during rotation to hold the log above the path of -- 10 - '' ~otj~9~ :
the pusher dogs 20. When rotation is completed, the rolls are lowered to place the log in the path of pusher dog 20. Motor 32 drives chain 18 to carry one of the pusher dogs 20 into engage-ment with a lower part of the rear end of a log, thus moving the log toward the saw. At this stage, one of the forward hold-back dogs 50 is positioned in the path of the advancing log. Before a large log engages the dog 50, it will actuate the limit switch 80 to actuate the hydraulic cylinder 64 and raise the frame 59, -~ ;
chain 52 and the hold-back dog 50. The upper part of the forward end of the log then comes into engagement with the hold-back dog 50 which is prepositioned in the path of the log. The dog 50 resists movement due to the friction in its supporting and driving means and the presence of the deactivated motor 82, thus imposing on the log a rearward force which places the Iog under longitudinal compression and tends to clamp the log firmly between a hold-back dog 50 and a pusher dog 20. Being positively ~ ~-clamped in this manner, the log acts as a rigid torsional re~
sisting beam as it is advanced through the bands 2 and 4 of the `
saw. As one of the two hold-back dogs 50 moves with the log, the other dog 50 is carried by chain 52 in a direction toward its log-receiving position. The sawèd log is supported on the rail ~ ~
84 and the slabs fall onto the screw rolls 86, to be carried - -- under the bridge section of the outfeed system by cross transfer chains, and to a slab resaw. If a reverse even index of sIabs passing to the slab resaw is desired, the screw rolls may be replaced by slab-receiving short driven belts or slat bed -sections which carry the slabs to camel back chains passing under the bridge section of the outfeed system.

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The stabilizer rolls 88 and 90 retain the log on the rail 84, and the forward lug 50 actuates the limit switch 94. This energizes the hydraulic motor 82 and drives the chain 52 to move the hold-back dog 50 forwardly away from the log. When one of the dogs 50 on chain 52 comes to the limit switch 96, the switch 96 is actuated to deactivate the hydraulic motor 82, thus leaving a dog 50 in a position where it may engage the next log to be -handled by the system.
Those skilled in the art will realize that many of the -~
:~ ' advantageous concepts of the invention may be utilized by appaxa-tus other than the specific embodiment disclosed herein. Various `~
types of means may be used to support the log before and after '`
sawing, and some aspects of the invention may be utilized without ``
the endless chains 18 and 52 for supporting and transmitting the ~ -- driving forces to the dogs 20 and 50. Vertical adjustability of the upper chain is desirable but not essential in all systems. , In view of the vast possibilities of modifying the system without departing from its important inventive concepts, it is emphasized -that the invention is not limited to the disclosed embodiment but encompasses other modifications and variations thereof which fall .~:
within the spirit of the following claims.

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¦~ The m~di~icatlon illustrated in Flg. ~ lncludes a ~ versal of elements shown in the emvodiment of Figs. 1-4, ln ¦Ithat the pusher dogs 102 are located on an upper endless carrler chaln 104 and the hold-back do~s 106 are located on a lower endless carrier chain 108~ The chaln 104 is supported on sprockets 110 and is posltlvely driven by a motor so that the pusher dogs 102 will enga~e the rear end o~ a log and drlve it forwardly from the infeed side to the outfeed s~de Or the twin band saws 112. A~ the log is belng driven, its forward end /o ls engaged wlth one o~ the hold-back dogs 106 on the lower ~ :
. forward carrier 108, the latter being retarded by a drag means such as brake-~r a deactivated hydraulic motor so that the log 111 be firmly engaged between the dogs 102 and 106. Arter a ~ :
og has completed its pass through the saws 112, the slabs r other side pieces fall onto the takeo~f rolls 114 and the ant remains on the center support member 116, being prevented ~rom falling ~herefrom by the ~lange wheel rollers 118 on the lvoted arms 120. A dr~ve motor is then activated to drive one f the sprockets 122 and carrier chain 108, moving the rorward ~o old-back dog 106 away from the log, bringlng another one o~ the old-back dogs 106 or chain 108 ~n~o a position in the pa~h o~ -he forward end of thè next lo~ to be passed through the ap~aratus.
The embodiment o~ Flg. 5 ls constructed to receive logs ~ dlfrerent diameters. The pusher dogs 102 and the~r carrler : 04 are vertically ad~ustable, such ad~ustment being made by ctuatlon o~ the hydraulic cyllnders 124 which vertically mov~
~he sllde blocks 126 which are af~ixed to the support beam 128 ~or sprockets 110. The slide blocks 126 are supported on a track ~30 whlch ls located on the stationary vertical pedestal3 132.

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Another reature Or the Flg. 5 embodlment ls that the longitudlnal axis o~ the inreed log ~upport such a~ turning rolls 134 may be slewed so that t:he axis Or a supported log is not coincldent with khe llne of movement of the dog~ 102 and o6 . This per~its taper sawing if desired to maxlm~ze the lumber yield rrom a glven log. Such slewing movement is provided by the hydraulic cylinde:rs 136 whose rods are connected by members 138 to the support platform 140 of the turning rolls 134. The upper surface of a statlonary support plate 142 slldin~ly :
~D supports the members 138.
. As an aid to the operator of the cylinders 135, the apparatus of Fi~. 5 is provided with light beam pro~ectors 144 which create spots of light on the leading and tralling ends o~
a log positioned on the rolls 134. The pro~ected beams of light are parallel to the path established by the dogs 102 and ~
106, and they pre~erably are in direct al~gnment with the ~ :
cutting portions of the saw blades. An operator may observe the location of the spots o~ llght on a log and àd~ust the ~ position of the rolls 134 to ~udge the appropriate position of `:

.i ~o the log. ~ c~urse, the pro~ectors 144 between the turning :
: rolls 134 and the saw blades must be provided with a retracting means which removes them from the path Or the log as it ~ :~
approaches the saw. ;
In some situatlons, it may be deslrable to provide a ' means for lowering the plate 140 and turnlng rolls 134 a~ter a :
log has been en~aged between the dogs 102 and 106. Thls may become particularly important when the axes o~ the turning roll~ :
134 and the longitudlnal axis Or a log thereon are slewed s~gnificantly w:lth respect to the path of the dogs 102 and 104.
~c Such downward retractlon wou~d remove the forward portlonæ o~
the turning rolls 134 rrom the path of the trailing portion Or a log moving toward the saw. - .
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The term "logs" as used ln thls specl~lcatlon rerers to jlarge longltudinally elongated bodies Or wood, lncludlng unsawn ¦logs and cants.

Claims (15)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A sawmill log handling system for advancing logs longitudinally along a given path from an infeed side of a saw, through the saw and to an outfeed side of the saw, said system comprising, rear log engaging means for engaging a rearward end of a log, rear drive means for moving said rear log engaging means along said given path to carry said logs from said infeed side, through the saw and to said outfeed side, forward log engaging means for engaging a forward end of said log while said log is being moved by said rear drive means, said forward log engaging means being movable from the infeed side to the outfeed side as the log is cut by the saw, and means for moving one of the log engaging means vertically to accommodate logs of different diameters.

2. The sawmill log handling system of claim 1 having an upper frame, one of said log engaging means being supported on said upper frame, and spaced apart bellcrank means supporting the upper frame for vertical movement.

3. A sawmill log handling method for advancing logs longitudinally along a given path from an infeed side of a saw, through the saw and to an outfeed side of the saw, said method comprising the steps of, placing the log in a position wherein its longitudinal axis is substantially parallel to said given path, engaging a rearward end of a log with a rear member which is supported on a first carrier, driving said first carrier means to move the rear member along said given path to carry said logs from said infeed side, through the saw and to said outfeed side, engaging a forward end of said log with a forward member on a second carrier, said driving step forcing the log against the forward member to move said forward member from the infeed side to the outfeed side, and sawing the log as it is moved from the infeed side to the outfeed side.

4. The method of claim 3 including the step of retarding the movement of the forward member during sawing to grasp the log between the driven rear member and the retarded forward member.

5. The method of claim 3 including, prior to engagement of the forward end of the log with said forward member, sensing the elevation of the forward end of the log, and moving the forward member vertically in response to the sensed elevation.

6. The method of claim 3 including, after said sawing step, the step of accelerating the forward member to move it forwardly out of engagement with said forward end of the log.

7. The method of claim 6 including, concurrently with the accelerating step, moving another forward member to a position which-lies in the path of the next log to be subjected to the method.

8. A sawmill log handling method for advancing logs along a machine axis from an infeed side of a saw, through the saw and to an outfeed side of the saw, said method comprising the steps of, placing the log in a position wherein its longitudinal axis is substantially parallel to said machine axis, engaging a rearward end of the log with a rear member, driving said rear member along said machine axis to move said log forwardly along the machine axis, engaging a forward end of the log with a forward member, said driving step forcing the log against the forward member to move said forward member forwardly along the machine axis, imposing a rearward force on the forward member during its forward movement to clamp the log between the rear member and the forward member, sawing the log as it is engaged by both members and moved forwardly along the machine axis.

9. The method of claim 8 including the step of vertically moving the rear member to align its path with the rear end of a log before engaging the log with said rear member.

10. The method of claim 8 including the step of chipping the log with a chipper head to provide a planar surface thereon as the log is engaged by both members and moved forwardly along the machine axis.

11. The method of claim 8 including, after said sawing step, the step of accelerating the forward member to move it forwardly out of engagement with said forward end of the log.

12. The method of claim 11 including, concurrently with the accelerating step, moving another forward member to a position which lies in the path of the next log to be subjected to the method.

13. The method of claim 8 including the step of supporting the log on the infeed side of-the saw before engaging the log with said rear member, and displacing the axis of the log from the machine axis before engaging the log with said rear member.

14. The method of claim 13 wherein the displacing step-orients the log axis at an angle to said machine axis.

15. The method of claim 13 wherein the displacing step positions the log axis laterally of the machine axis.