Note: Descriptions are shown in the official language in which they were submitted.
This inven~lon relates to sawmill apparatus and methods,
and particularly to a log handling sy~tem 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 chain carrler provided wi~h
pusher dogs which push the logs through circular saws or
opposed band saws. On the outfeed side of the sa~s, ;
upright guides called "splittersl' 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 heretorore 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 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 i5 used to apply
a gripping force bet~eeD ehe log-engaging ~eans.
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The present inveneion represents a signi~icant
advance over the prior art systerns 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 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 produc-ts, 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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and sold at moderate prlces~ thus making it available to
a large variety of sa~nill operators.
Another obJect i8 to proYlde a system which i5
extremely compact and does not require ~n e~cessive amount
of mill space.
Other ob~ects o~ the invention are to provlde a
system which is extremely fast due to lts avoidance o~
the necessity of troublesome components such as splitter~
or chipper heads; to provide a system capable of handling
/G hard ~ood, soft wood or frozen stock; and, to provide a
.
system IJhich is due to its relative simpliclty and
automatic features does not require an experienced
operator. ~`
Varlous ones o~ the preceding ob~ects of the
invention are attributable to one or more of the inventlve
concepts utilized in the preferred embodiment o~ the
invention disclosed in this speclfication.
One of the inventive concepts relates to the u~e
o~ a driven lcg-engaging me~ns operable on the rear or
2~ trailln~ end o~ a lo~, together with a ~rward log-en~Rging
mean~ which engages the for~ard or leading end of a log
and is supported on a chain or other endles~ carrier
positioned a~ove the path of the lo~. Another in~entlve
concept involve6 the use of a driven rear log-engaglng mean~,
and a folward log-engaginG me ns which has its movement ~ ~
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reta~ded as a log is advanced through a saw, whereby the log
is grasped during sawing betw~en 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 inventive 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 f~r engaging a
rearward end of a log, first carrier mea`ns attached to and
supporting said rear log engaging means, rear drive means for
moving said ~irst carrier means to advance the rear lo~ 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 sa~d 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 forward drive means for driving the forward log
engaging means forwardly away from the log after the log is
. cut by the saw.
A typical preferred system embodying all of the inventive
~ 30 concepts is disclosed in the accompanying drawings wherein~
: Fig. 1 is a perspective view, diagramatic in same
respects, of the log handling system of the Invention~
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Fig. 2 is a side eleyation of the s~stem of Fi~
Fig. 3 is a plan view o~ the lo~ handling system ~f
Fig. l; -
Fig. 4 is a sectional vlew 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 cut a
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log whicn is advanced longitudinall~ therethrough, the sldes
o~ the log being cut by the ad~acent vertical portions o~
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
~or producing a heart piece of a thickness ranging from
about four inches to any larger size which may ba accommodated
by secondary reduction resaws a~ailable at the mill. Of
course, any nu~ber 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 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 eleva~ed 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 i5 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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and the chain is engaged on a series 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
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
10 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
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 guiderail 54 as shown in Fig. 4.
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The upper frame 59 ia vertically movable to permit the dogs ~`
50 to engage the upper part of the forward end of a log at
an appropriate elevation. This 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 axle 70. The vertical arm of
the bellcrank lever 68 ij 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 ~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 hydra~lic
cylinder 64. It will be observed ~hat 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-tor who 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 per~ormed 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
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diameter, thus sensing the elevation of a forward end of
a log prior to engagement o~ the l~g ~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 height.
During the sawing operation, firm engagement o~
the hold-back dogs 50 with the log is assured by retarding
the movement oE the dogs 50 as the ~og 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 S0. 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 purpose5 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 ~ith 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 ;
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completion of sawing, the slabs will fall onto the con-
ventional 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 sha~ts 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 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 arrîves at and trips the limit switch 96
positioned at the rear end of the upper frame 59. This
deac~ivates 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 rotatPd by
an hydraulic ~otor (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
pusher dogs 20, ~hen 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 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 ~hich 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
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clamp the log firmly between a hold-back dog 50 and a pusher ~ -
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dog 2Q. 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 sa~. 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
posi~ion. The sawed log is supported on the rail 84 and
the slabs fall onto the screw rolls 86, to be carried
under the brid~e section of the outfeed ~ystem by cross
transfer chains, and to a slab resa~. If a reverse even
index of slabs passing to the slah resaw is desired, the
screw rolls may be replaced by slab-receiving short driven
be~ts or slat bed sections ~hich 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 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 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 drivi~g forces
to the dogs 20 and 50. Vertical adjustability of the upper
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588
chain is desirable but not essentlal ~n all systems. In
view of the vast possibilities of modif~ing the system
without depart~ng 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 ~ithin the spirit of the
follo~ing claims.
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i~S~38
The modification illustrated in Fig. 5 includes a
reversal of elements shown in the embodiment of Flgs. 1-4, in
-that the pusher dogs 102 are located on an upper endless carrie~
chain 104 and the hold-back dogs 106 are located on a lower
~endless carrier chain 108. The chain 104 ls supported on
sprockets 110 and is positively driven by a motor so that the
pusher dogs 102 will engage the rear end of a log and dr~ve
t ~orwardly ~rom the lnfeed side to the outfeed side Or the
twin band saws 112. As the log ls belng driven, lts ~orward end
is engaged with one Or 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
ill be rirmly engaged between the dogs 102 and 106. After a
¦log has completed its pass through the saws 112, the slabs
~r other side pleces fall onto the takeorf rolls 114 and the
ant remains on the center support member 116, being prevented
~rom falling therefrom by the flange wheel rollers 118 on the
~lvoted arms 120. A drive motor is then activated to drlve one
~r the sprockets 122 and carrier chain 108, moving the rorward
~old-back dog 106 away ~rom the log, bringin~ 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 throu~h the ap~aratus.
The embodiment Or Fig. 5 is constructed to receive lo~s
D~ different diameters. The pusher dogs 102 and their carrie`r
~04 are vertically adJustable, such ad~ustment- bein~ made b~
actuation of the hydraulic cyllnders 124 whlch vertically move ~ ~
~he sllde blocks 126 ~hich are afflxed to the support beam 128 ror: ~ -
~prockets 110. The--slide blocks 126 are supported on a track
130 which is located on-the statlonary vertical pedestals 132.
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Another feature Or the Fig. 5 embodi~ent 18 that the
longitudlnal axis Or the lnfeed log suppor~ such a~ turning
rolls 134 may be slewed so that t'he axis of a supported log
is not coincident wlth the line of movement Or the dogs 102 and
106. This permits taper sawing lr desired to maxlmize the :
lumber yield ~rom a given 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 o~ a stationary support plate 142 slidlngly
/D supports the members 138.
As an aid to the operator o~ the cylinders 136, the ~;:
apparatus of Fig. 5 is provided with light beam pro~ectors 144 -
which create spots o~ light on the leading and traillng ends o~
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 pre~erably are in direct alignment with the .
cutting portions of the saw blades. An operator may observe .~: :
the location o~ the spots o~ ht on-a log and ad~ust-the
position o~ the rolls 1~4 to ~udge the appropriate position Or
the log. 0~ course, the proJectors 144 between the turning
rolls 134-and the saw blades must be provided with a retracting - ::~
means.which-removes them ~rom the path o~ the log as it `~
approaches the-sa~.- - - -
In some situations-~--it-may-be desirable-~o provide a .' :
means for lowering-the plate 140 and turning rolls-134 a~ter a
log has been-engaged-between the dogs 102 and -106. This may ~ :
: become particularly important when the axes o~ the turnin~ rolls . .
134 and the lon6itudlnal axis o~ log thereon are ~lewed
signlricantly with respect to the path of the dogs-102 and 104.
30 Such downward retractlon would remove the ~orward portions Or ~.:
the ~urnlng rolls 134 ~rom the path of the traillng portlon Or a -
log-movlng toward the saw. .
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The term "loKs" as used ln this specificat~on rerers to
large longltudinally elongated bodies Or wood~ lncludlng unsawn
logs and nts.
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