CA1066589A - 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 does 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

5~
This invention relates to sawmill apparatus and methods, and particularl~ to a log handling system which engages and advances logs accurately through a saw; even in in~tances 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 chain carrier provided with pusher dogs which push the logs through circular saws or opposed band saws. On the outfeed side of the sa~s, .
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 sawing of small short logs of essentially cylindrical chracteristics.
It has been recognized heretofore that logs of var~ing 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 rear 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.

- 2 -The present invention represents a signiflcant ~ ,.. .
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 ~-sp~itters 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 sized sawmill operator.
One ob~ect of the invention is to hold logs under positive control during sawing, 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 due to their limb or knot projections, crooks, sweep, swell, rotten hearts, angled or splintered ends and other flaws.
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 : ' ..:.
.: ."~ ':

~ 3 ~
.. '~:
';' ~

58~

and sold at moderate prices, thus making 1t avaiLable to a large variety o~ sawmill operators~
Another ob~ect is to provide a system which is extremely compact and does not require an excessive amount of mill space.
Other o~jects of the invention are to provlde a system which i~ extremely fast due to its avoidance oE
the necessity of troublesome components such as splitters or chipper heads; to provide a system capable o~ handling hard wood, soft ~ood or froæen 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 objects 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 ~hich 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, and a forward log-engaging means ~hich has its m-ovement ~ .

1~ti589 retarded as a lo~ is advanced through a saw, whereby the saw is 4rasped during 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-engagin~ means away from the log after the sawed log ~s held on its support by a stabilizer means. A further inventive concept is d~rected t~
a vertically adjustable forward log-engaging means which is moved vertically in response to signals from a sens~r for detecting the elevation of the forward end of a log.
In accordance with one broad aspect, the invention relates to a s~wmill 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, 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 ~or -movement from an initial position a~ the infeed side of the saw to the outfeed side of the saw as said log is cut by the saw, and an hydraulic motor connected to said second carrier, said hydraulic motor being deactivated to retard m~vement of the forward log engaging means as the log is advanced through the saw by the rear drive means. `
A typical preferred system em~odying all of the inventive concepts is disclosed in the accompanying drawings wherein;
Fig. 1 is a perspective view, diagramatic in some respects, ;
i. ~ ' ''".

';'`. ,, -. --, - - . . ~, - . -~0~5~3~

of the log handling system of the in~ention;
Fig. 2 is a side elevati~on of the-system o~ ~ig~
Pig. 3 is a plan view of the log handling system of Fig. l;
Fig. 4 is a sectional view thereof as seen along the line 4-4 in Fig. 2; and ~ig. S is a perspectiYe view of a ~odifiea log h~ndling system. `~
Thro~ghout 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 cut a ., : .

'. -' ":

`-' ,:.
.
. ~

: .
SA ~ ;:

~' ~o~
log which is advanced longitudinall~ therethrough, the sides o~ the log ~eing 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 ~referably shifting saws for producing a heart piece of a thickness ranging from about four inches to any larger s~ze which may be accommodated by secondary reduction resaws avallable 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 a~d 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 ~ith a log and they are rotatable abaut 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 belo~. , 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 ~ollowed by logs in the apparatus. This chain 18 serves as a lower carrier for supporting a series of rear log engaging m2ans ,`
such as the pusher dogs illustrated at 20. The upper horizontal run of the chain 18 rides on guide rail 22 ~. '.''' -:
;`~
- , ~. .
' :, . :: : ~ . : , ,, -- - ., ,, . . " :

ti65~3~
and the chain is engaged on a series of sprockecs 24, 26~
28 and 30, the latter being shown only ln 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 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 gîven path in the direction indicated by the arrow 48. This carries the log through the saw and ``~
, to the outfeed side of the sa~
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 ta support the guiderail 54 as shown in Fig. 4.
': ' '~ ~ ' ' `,. ,:

' ~ " - -s89 The upper frame 59 i~ vertically m~vable t~ permit the dogs 50 to engage the upper part of the for~ard end of a log at an appropriate elevation. Thi5 vertical movement is produced by a hydraulic cylinder 64 which has its plunger rod 66 connected at 67 to the frame 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 7~4, the latter ~eing 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 hydraylic cylinder 64. It ~ill be observed tha:t 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 opera~or ~ho observes the e~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 log comes into contact with a hold-back dog 50. The actuator of limit switch 80 will be contacted by a log of large ` ,',': ~

`;

~:

i~ '` ' ` ' ` ' '` " ' ' ' .. `'' ' ' ' . ` '; `' ` ' ~' '.`. ' ' ` " ~ ' ' ' ' " ' ` ' '` ' ` ` ' ` " ' ` .
' ' ' ' ', . ' : ' ' `.' `.'. ' ' .'`"

:~O~i~i5~39 diameter, thus sensing the elevation of a forward end of a log prior to engagement of the log ~ith 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 he~ight.
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 sa~ 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 ~he -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 b~ 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 shaft5 for chain 52. Initial engagemen~ of the hold-back dog 50 ~ith the log may be achieved by momentarily reversing the motor 8Z.
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 _ -... . ...... -` iL0~65~39 completion of sawing, the slabs will fall onto the con-ventional scre~ rolls 86 ~hich are provided ~ith helical ribs (not shown) and are rotated about their axes to move the slabs in the directions lndicated by the arrows 87.
The flitch or cant is held or retained on the upper edge of the rail 84 b~ the rolls 88 and 90 which are stabilizer means for retaining the log on the log support rail 84 to prevent lateral displacement af 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 s~inging 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 motor 82 drives the `
chain 52, moving the dogs 50tforwardly 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 àrrives at and trips the limit switch 96 positioned at the rear end 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 ~
"' , , . :
" ', ~ ' ;~, ` 30 ~ ~ ~
. ~' .

iS~3 rolls 14 and 16 by a conventional log deck which has a log stop and loader. The rolls 14 and 16 are rotated b~
an hydraulic motor (not shown) to place the log at an appropriate orientation. The rol:Ls 14 and 16 are elevated during rotation to hold the log above the path of 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 engagement ~ith a lower part of the rear end of a log, thus moving the log to~ard the saw. At this stage, one of the forward hold-back dogs SQ is positioned in the path of the advancing log. Before a large log engages the dog 50, it will actuate the li~it switch 80 to ac~uate 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- ;
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 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 resisting beam as it is advanced through the ~ands 2 and 4 of the sa~. As one of the two hold-back dogs 50 moves with the log, the other dog 50 is ~' ~

' 30 `~

S8~a carried by chain 52 in a direction toward it~ log-receiving posîtion. The sawed log is supported on the rail 84 and the sla~s fall onto the screw rolls 86, to be carried under the bridge section of the outfeed system by cross trans~er chains, and ~o a slab resaw. If a reverse even index of slabs passing to the slab resa~ is desired, the screw rolls may be replaced by slab-receiving short driven - ;
belts or sla~ 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 ~orwardly away from ;
the log. When one of the dogs 50 on chain 52 comes to the limit s~itch 96, the s~itch 96 is actuated to deactivate the hydraulic motor 82, thus leaving a dog S0 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 investion 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 tr~nsmitting the driving forces to the dogs 20 and S0. Vertical adjustability of the upper .. . .

' : -~. . . . . .. - . . .

- : ~ . ~ . : . .

chain is desirable but not essential ln all systems. In vie~ oP the vast posslbilities of modif~ing 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 ~hich fall ~ithin the spirit of the ~ .
follo~ing claims.

': , .~,' ' .~ :

,'`,., ' `'' -.

-, `' .

- 13 - :` .
~ '' "' ' :~ , . - -,: , : . . , .; :

-~ ~
1 1~51~39 The modlfication illustrated in Flg. 5 lncludes a reversal Or elements shown in the embodiment Or F~gs. 1-4, ln that the pusher dogs lQ2 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 positively driven by ~ motor so that the pusher dogs 102 will engage the rear end of a log and drlve it forwardly ~rom the infeed s~de to ~he outfeed side of' the twin band saws 112. As the log is being driven, its ~orward end /~ ls engaged with one of the hold-back dogs 106 on the lower . : .
forward carrier 108, the latter being retarded by a drag means ~ ~
such as brake-'~or a deactivated hydraulic motor so that the lo~ ~ :
will be firmly engaged between the dogs 102 and 106. After a log has completed its pass through the saws 112, the slabs r other side pieces fall onto the takeof~ rolls 114 and the ant remains on the center support member 116, belng prevented ~ :
~rom falllng thererrom by the ~lange wheel rollers 118 on the ivoted arms 120. A drive motor is then activated to drive one .
f the sprockets 122 and carrier chain 108, moving the rorward ~o lold-back dog 106 away ~rom the log, bringing another one o~ the : old-back dogs 106 or chaln -108 into a position in the path of ~ ~
he forward end of the next log to be passed through the ap~aratu5. `
- The embodiment-of Fig. 5 is constructed to receive logs -~
. f dlf~erent diameters. The pusher dogs 102 and thelr carrier . 04---are-vert~cally ad~ustable,-such ad~ustment being made ~y ctuation o~ the hydraulic cylinders 124 whiCh vertically move ~he slide bloc~s 126 which are 8f~ixed to the support beam 128 ror prockets 110. The sllde blocks 126 are supported on a track ~30 which 1 ocated on the stati~nary vertical pede~tsl~ 132.

:~ -14-.; . ~ : ~ - : - . .; . -1~6589 Another f'eature of the Fig. 5 ernbodlment is that the lon~itudinal axis o~ the lnfeed log support such as turning rolls 134 may be slewed ~o that the ax~s of a supported log not coincident with the line of movement o~ the dogs 102 and 106. This permits taper sawing if desired to maximize the lumber yield rrom a given log. Such slewing movement is provlded by the hydraul~c cyllnders 136 whose rods are connected by members 138 to the support platform 140 of the turning rolls 134. The upper sur~ace of a stationary support plate 142 slidingly ~c supports the members 138.
. As an ald to the operator of the cylinders 136, the .
apparatus of Fi~. 5 is provided with light beam pro~ectors 144 which create spots of llght on the leading and trailing ends of a log posit~oned on the rolls 134. The pro~ected beams o~
light are parallel to the path establlshed by the dogs 102 and 106, and they preferably are in direct al~gnment with the cutting portions of the saw blades. An operator may observe the location Or the spots Or light on a log and ad~ust the .-posltlon of the rolls 134 to ~udge the appropriate position o~
. ~o the log. or course, the pro~ectors 144 between-the turning . rolls 134 and-the saw blades must be provided wlth a retrac~ing ~ .
.- means--which removes-them--from-the path of the-log~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 ha~ been engaged between the-dogs-102 and 106. This may .~ become particularly important when the axes o~ the turning-rolls ~
134 and the longi~udlnal axis Or a log thereon are ~lewed ~ ::
... slgnificantly with respect to the path o~ the dogs 102 and 104. .
.~o Such downward retraction would remove the ~orward portlons Or -.;: the turnlng rolls 134 rrom the path Or the trallin6 portion Or a .
. log movln~ toward the saw. ~

-15- 1 :
, 1 1~t;6~

The term "logs" as used ln this specificatlon rerers to 12rge longitudinally elon~ated bodles o~ wood, including unsawn logs and cants.

.

Claims (6)

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, 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 an hydraulic motor connected to said second carrier, said hydraulic motor being deactivated to retard movement of the forward log engaging means as the log is advanced through the saw by the rear drive means.

2. The sawmill log handling system of claim 1 wherein said second carrier means is an endless member movable in a continuous path.

3. The sawmill log handling system of claim 1 having means for activating said hydraulic motor after a log is cut by the saw to move a said forward log engaging means to said initial position to receive a subsequent log.

4. The sawmill log handling system of claim 3 wherein said second carrier means is an endless member movable in a continuous path.

5. The sawmill log handling system of claim 2 having means for activating said hydraulic motor after a log is cut by the saw to drive the forward log engaging means forwardly away from the log.

6. The sawmill log handling system of claim 5 wherein said second carrier means is an endless member movable in a continuous path.