Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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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.
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The present invention represents a signiflcant
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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
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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
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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, ;
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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
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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
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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 ``~
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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.
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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.
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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
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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
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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
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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 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
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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
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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.
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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.
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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. ~
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The term "logs" as used ln this specificatlon rerers to
12rge longitudinally elon~ated bodles o~ wood, including unsawn
logs and cants.
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