CA1066590A - 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

itis9a3 This invention relates to sawmill apparatus ancl methods, and particularly to a log handling system which 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 chaLn carrler 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 inaccuracies inherent in such systems restrict their practical use, where accuracy is important, to the sa~ing of small short logs of essentially cylindrical chracteristics.
It has been recognized heretofore that logs of varying lengths may be accurately sawed by engaging their opposite ends by members which apply a gripping force ~' thereto. U.S. patents 3,503,428 and 3,731,578 to Bo Ingemar Ackerfeldt disclose this general concept in highly com-plicated systems which are far more complex and expensive -than the present invention. Ackerfeldt suspends his forward and rPar log-engaging means from a common overhead track; both log-engaging means are coupled to and disengagable from a common drive cable; and, a spring is used to apply a gripping force between the log-engaging means.

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The present invention represents a significant advance over the prior art systems described above. Unlike the prior skrag saws, logs of irregular shapes may be sawed accurately, and the necessity for the often-troublesome splitters is avoided. It is superior to the Ackerfeldt system due to its relative simplicity which makes the apparatus more compact, simpler to operate, less expensive to manufacture and sell, and thus more accessible to the small or medium si~ed sawmill operator.
One ob~ect of the invention is to hold logs under positive control during sawi,ng, thus providing a degree of safety and accuracy which cannot be attained 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 through many existing systems duelto their limb or knot projections, crooks, sweep, swell, rotten hearts, angled or splintered ends and other fl'aws. ~`
Still another object of the invention is to ~
produce completely accurate products, usually flitches, to --provide a maximum recover of lumber even from poor quality logs~
A further object of the invention is to provide a system which may handle a random mix and sequence of logs `-of varying lengths and diameters.
Another object is to provide a system which is relatively uncomplicated so that it may be manufactured :. :,' -.~
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~O~i59() and sold at moderate prices, thus making it available to a large varlety o~ sawmill operators, Another ob~ect is to provide a system which is extremely compact and does not require an excessive amo~lnt of mill space.
Other obJects oE the invention are to provide a system which is extremely fast due to its avoidance of the necessity of troublesome components such as splitters or chipper heads; to provide a system capable of handling ;~
hard wood, soft wood or frozen stock; and, to provide a .:
system which is due to its relative simplicity and automatic features does not require an experienced operator.
Various ones of the preceding ob~ects of the ~
invention are attributable to one or more of the inventive ` ~-concepts utilized in the preferred embodiment of the invention disclosed in this specification.
One of the inventive concepts relates to the use of a driven log-engaging means operable on the rear or "
trailing end of a log, together with a forward log-engaging means which engages the forward or leading end of a log and is supported on a chain or other endless carrier positioned above the path of the log. Another inventive concept involves the use of a driven rear log-engaging means, ~ ;
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- and a forward log-engagîng means which has its movement .~ :

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retarded as a log is advanced throu~h a saw~ whereby the log is grasped during sawing between the driven rear log-engaging means and the retarded orward log-engaging means.
Still another inventive concept pertains to the arrang~men~ which advances the forward log-engaging means away from the log after the sawed lo~ is held on its support by a stabilizer means. A further inventive concept is directed to a vertically ad3ustable forward log~engaging means which is moved vertically in response to signals from a sensor ~or detecting the elevation o~ the ~orward end of a log.
In accordance with one broad aspect, the inventi.on relates to a s~mill log handling system for advancing logs longitudinally along a given axis ~rom 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, first carrier means attached to and supporting said rear log engaging means, rear drive means for moving said first carrier means to advance the rear log engaging means along said given path to carry said log from said infeed ~;
side, through the saw and to said outfeed side, forward log engaging means for engaging a ~orward-end of said log while said log is being moved by said rear drive meansJ second carrier - means for supporting one or more said forward log engaging means for movement from an initial position at the infeed side of the saw to the--outfeed side-of the saw as-said-log is-cut by the saw, and log support means on the infeed side of the saw for supporting a longitudinally oriented log ~or lateral movement with respect to said axis prior to its engagement--- by said log engaging means.
~ txpica;L pre~erred system ~mbodying all of the--inventive concep~s is disclosed in the accompanying drawings wherein:
Fîg. 1 is A perspective YieW~ diagramatic in some :, -.. --, : ~
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-10~590 respect, of the lo~ handling system o~ the invention;
Pig. 2 i~ a side elevation ~ the system of Fig~ l;
Fig. 3 is a plan view of the log handling system of Fig. l;
Fig. 4 is a s~ctional view 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 drawings, a twin bandsaw assembly is ;
shown in diagrammatic form 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 c~t a ; ~ --, ~, :; `:' ,~, ~--';.:. ~,'' :. :

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log which is advanced longitudinally therethrough, the sides o~ the log being cut by the ad~acent 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 preEerably shifting saws :., for producing a heart piece of a thickness ranging from ;
about four inches to any larger size which may be accommodated ; by secondary 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 `
~bout their longitudinal axes by a hydraulic motor so as to :. .
position a log preliminarily 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 logs 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 guide rail 22 .'-` , :
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: ' ` 3 and the chain is engaged on a series of sprockets 247 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 sprockets and guide rail 22 by a drive means including the hydraulic fluid motor 32. The sprocket 34 of hydraulic motor 32 is engaged l~ith the chain 18 b~ a reduction system illustrated in Fig. 1 and including the chain 36, enlarged sprocket 38, shaft 40, reduced sprocket 42, chain 44 and 10 the sprocket 46 which is coupled directly to the sprocket 28 for the chain 18. Operation of the hydraùlic motor 32 drives the chain 18 and its pusher dogs 2 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 20 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.

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:~o~sg(3 The upper Erame 59 i5 vertically movable to permit the dogs :
50 to engage the upper part oE the forward end of a log at an appropriate elevation. This vertical movement is produced by a hydraulic cylinder 64 which has its plùnger ~ .
rod 66 connectcd at 67 to the Erame 59 and to a horizontal leg of a bellcrank lever 68 which is pivotally mounted on - .
the rotatable stationery pivot ax:Le 70. The vertical arm of .
the bellcrank lever 68 is pivotal:Ly 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 béing ;
supported on a stationary pivot axle 76 and being connected ~.
to the frame 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 64. It ~ill be observed that an identical arrange- . .
ment 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 hydraulic cylinders 64 may be ' performed by a machine operator who observes the el~evation of the forward end of a log being fed toward the saw by the rear pusher dogs 20. However, this change in elevation may be performed automatically by providing a limit switch 80 at a location prior to a point where the forward end of a .
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log comes into contact with a hold-back dog 50. The actuator ~-of limit switch 80 will be contacted by a log of large .' .,; ~

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diameter, thus senslng the elevation of a for~ard end of a log prior to engagement of the log with the hold-back dogs 50. ~ctuation oE the limit switch 80 will a~tomatically operate hydraulic cylinder 64 to elevate the frame 59, thus moving the chain 52 and dogs S0 to an approprlate height.
During the sawing operation, firm engagement of the hold-back dogs 50 with the log is assured by retarding the movement 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 20 and the hold-back dogs 50. The retardation of the hold-back dogs 50 is achieved by resistance means which includes the friction of the means for supporting 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 reversing 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 _ g -- .:

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completion oF sawing, the slabs ~ill ;Eall onto the con- -ventional screw rolls 86 which are provided ~ith 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 ~8 and 9~ 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 required. `~
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 motorl82 drives the chain 52, moving the dogs 50 forwardly away from the log when the log i5 retained by the stabilizer rolls 88 and 90.
The hydraulic motor 82iis deactivated when one of the hold~
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back dogs 50 arrives at and trips the limit switch 96 positioned at the rear end of the upper frame 59. This :
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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 ~ ,.
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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 (not 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 the p~sher 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 engagement with a lower part of the rear end oE a log, thus movîng 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 S0, 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 support~
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ing and driving means and the presence of the deactivated motor 82, thus imposing on the log a rearward force which - places the log under longîtudinal 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 resisting 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 -~

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carried by chain 52 in a direction toward its log receiving ~ ~i position. The sawed log is supported on the rail 84 and the slabs Eall onto the screw rolls 86, to be carried under the bridge section of the outEeed system by cross ;
transfer chains, and to a slab resaw. If a reverse even index of slabs 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.
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 comea to the ' limit s~itch 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 apparatus 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 ,, :

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chain is desirable but not essential in all systems. In view of tlle 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 embodi~ent but e~lcompasses other modifications and variations thereof which fall within the spirit of the following claims.

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The modification illustrated in Fig. 5 lncludes a reversal ~f elements shown in the embodlment of Figs. 1-4, in that the pusher dogs 102 are located on an upper endless carrier chain 104 and the hold-back dogs 106 are located on a lower endless carrier chain 108. The chain 104 is supported on sprockets 110 and is positlvely driven by a motor so that the pusher dogs 102 will engage the rear end of a log and drive ~t f~rwardly rrom the infeed side to the outfeed side o~ the twin band saws 112. As the log is belng driven, its forward end ~o ls engaged with one o~ the hold-back dogs 106 on the lower ~orward carrier 108, the latter being retarded by a drag means such as brake ~r a deactivated hydraullc motor so that the log will be firmly engaged between the dogs 102 and 106. After a og has completed its pass through the saws 112, the slabs Dr other side pieces fall onto the takeof~ rolls 114 and the ant remains on the center support member 116, being prevented ~rom ~alllng therefrom by the rlange wheel rollers 118 on the ~lvoted arms 120. A drlve motor is then activated to drive one ~f the sprockets 122 and carrier chaln 108, moving the ~orward - ~o ~old-back do~ 106 away from the log, bringing another one of the ~old-back dogs 106 or chaln 108 into a position in the path o~
the rorward end o~ the nex~ log to be passed through the apparatus.
-The embodlment Or Fig. 5 ls constructed to receive logs ~ ~
: ~ D~ dlfferent dlameters. The pusher dogs 102 and thelr carrie`r ~, ~04 are vertically ad~ustable, such ad~ustment being made by actuation Or the hydraullc cylinders 124 which vertically move ~he slide blocks 126 whlch are a~ixed to the support beam 128 ror ~prockets 110. The sllde blocks l26 are supported on a track-30 whlch ls ooated on the ~tatlonary vertlcnl pede~ta1s 13Z.

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Another ~eature Or the Fig. 5 embodlment Is that the longitudinal axis Or the lnreed log support such as turning rolls 134 may be slewed ~o that the axis of a supported log is not coincident with the line O:r movement of the dogs 102 and 106. Th~s permits taper sawing i~ desired to maximize the lumber yield from a given log. Such slewing movement is provided by the hydraulic cylinders 136 whose rods are connected by members 138 to the support platform 140 Or the turntng rolls 134. The upper surface of a stationary support plate 142 slidingly ~o supports the members 138.
. As an aid to the operator o~ the cylinders 136, the apparat~s of Fi~. 5 is provided with llght beam pro~ectors 14~
which create spots of light on the leading and trailing ends Or a log positioned on the rolls 134. The pro~ected beams o~ :
light are parallel to the path established by the dogs 102 and :
106, and they preferably are in dlrect alignment with the :
cutting portions of the saw blades. An operator may observe the location of the spots o~ light on a log and ad~ust the :~
position o~ the rolls 134 ~o ~udge the appropriate posit~on Or ~o the log. Of course, 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 of the lo~ as it approaches the saw.
In some situations, it may be desirable to provide a ` . .
means for lowerln~ the plate 140 and turning rolls 134 a~ter a log has been engaged between the dogs 102 and 106. This may become particularly lmportant when the axes o~ the turning rolls 134 and the lon~ltudlnal axi~ o~ a log thereon are slewed slgniricantly with respect to the path o~ the dogs 102 and 104. .
Such downward retraction would remove the ~orward portions o~
: the turning rolls 134 rrom the path Or the trailing portion Or a .

log moving toward the saw.

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10~5~6 The term "logs" as used in this speci~catlon re~erR to large longitudlnally elongated bodies Or wood, lncludi~g unsawn logs and cants.
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Claims (8)

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 axis 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, first carrier means attached to and supporting said rear log engaging means, rear drive means for moving said first carrier means to advance the rear log engaging means along said given path to carry said log 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, second carrier means for supporting one or more said forward log engaging means for movement from an initial position at the infeed side of the saw to the outfeed side of the saw as said log is cut by the saw, and log support means on the infeed side of the saw for supporting a longitudinally oriented log for lateral movement with respect to said axis prior to its engagement by said log engaging means.

2. The sawmill log handling system of claim 1 wherein said carrier means are endless members movable in a continuous path.

3. The sawmill log handling system of claim 1 wherein the first carrier means is located above said axis and the second carrier means is located forwardly of the support means.

4. The sawmill log handling system of claim 3 wherein said carrier means are endless members movable in a continuous path.

5. The sawmill log handling system of claim 1 wherein said log support means is operable to move a log thereon to a position where the axis of the log is not coincident with said given axis.

6. The sawmill log handling system of claim 5 wherein said carrier means are endless members movable in a continuous path.

7. The sawmill log handling system of claim 5 wherein the first carrier means is located above said axis and the second carrier means is located forwardly of the support means.

8. The sawmill log handling system of claim 7 wherein said carrier means are endless members movable in a continuous path.