Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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MACHINE FOR REDUCING LOGS
BACKGROUND
This invention concerns a decortication or
debasting machine for reducing raw logs to a reference
cross-section along the length of the log.
Current machines for debarking, decorti-
cating, or debasting logs have circular-shaped rotary
carriers which rotate around the logs as the logs pass
longitudinally through the machine. Swingably mounted
frames which are pivotably mounted on the rotary
carrier support cutter tools on one end. The other
ends of the swingably mounted frames are connected to
pneumatic cylinders which swing the frames and moVe the
cutter tools into contact with a log's surface. The
rotary carrier, through a series of ring gears, pulley
wheels, and V belts, turns the drive shafts of the
cutter tools.
Each cutter tool on such current machines
has a flanged, hollow axle junction through which the
drive shaft passes and is coupled to the drive shaft
through a universal joint. The cutter tools are
separately pivoted on guiding arms under spring tension
and are movable within certain bounds in a direction
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opposite to the guiding arms. This allows the cutter
tools to "give way" to unusual obstructions in their
paths such as large knots or root structures.
A machine of this type has been disclosed in
U.S. Patent 2,591,751 and German Patent 23 20 450.
An improved method for adjusting the cutting
tool to the raw surface of the log provides each cut-
ting tool holder with a special pivoting axis per-
pendicular to the swinging axis of the cutter tool.
This special pivoting axis allows the cutting tool to
be pressed against and maintained in contact with the
surface of the log over the entire length of the log.
Current machines which employ this latter
method have several swingable cutting tools which are
pivotably mounted on parallel axes and are held against
the log over its entire length. Such machines, how-
ever, cannot reduce or debark differing cross-sections
of a log having root bulges or larger protuberances and
produce a properly finished cross-section that is
consistent throughout the length of the log. The
cross-sectional shape of the decorticated or debarked
log at any point differs only insignificantly from the
cross-sectional shape of the raw log.
Before logs debarked by current machines can
be processed further in a sawmill it is necessary to
remove the root bulges and larger protuberances. This
requires a special working step of using a chisel or
chipping tool which reduces that section of the log to
a cylindrical form This, however, results in a waste
of both time and wood.
It is an object of this invention to provide
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a structure for producing finished logs with cross-sections that
correspond to a reference cross-section over substantially the
entire length of the log and, at the same time, maintain a high
production rate with a minimum loss of wood. In this respect,
in one embodiment about to be described, the "reference cross-
section" includes even generally non-circular cross-sections to
which a raw log may be reduced during the decortication or de-
basting process.
In accordance with the invention there is provided a
machine for reducing the cross-section of a log to a reference
- cross-section throughout at least part of the length of the log,
comprising a rotor frame work rotatable about the longitudinal
axis of the log, a plurality of tool holders fastened to the
rotor frame work, rotating milling tools each having a spin axis
orientated with an angle to the log axis and each being movably
connected to a corresponding tool holder, a pair of parallel
guide lever means connecting each milling tool to a correspond-
ing tool holder, the guide lever means each having pivot axes
perpendicular to a plane defined by the longitudinal axis of the
log and the rotation axis of the respective milling tool, actua-
tor means for swingingly moving each spinning milling tool towards
the log and runner means firmly coupled to each milling tool and
riding on a finished surface portion of the log for limiting
the cutting depth of the milling tools.
Adjustable guides or springs can be provided for limit-
ing the swinging motion of the decortication or debasting tools,
which in turn limits the depth of the cut, a continuous contact
with the dinished surface of that portion of the log just de-
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barked or debasted establishes the desired cutting depth.
The changes in the cross-section of the raw log can
be measured automatically by sensors and the information is
fed electronically to a control unit which regulates the ad-
vancing speed of the log and the cutting depth of the decorti-
cation or debasting tool.
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This invention provides a debarked or de-
basted log that can be automatically fed onto a sawmill
without further processing and with only a small
waste of wood.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other objects, features and
advantages of this invention will be apparent from the
more particular description of preferred embodiments
thereof as illustrated in the accompanying drawing.
The drawing is not intended to be to scale, but rather
is presented so as to illustrate principles of the
invention in a clear form.
In the drawing: FIG. l is a schematic cross-
section of a reducing machine embodying the invention.
Much of the peripheral structure has been removed to
better illustrate the machine's more significant
aspects.
DETAILED DESCRIPTION
One of a plurality of reducing mechanisms of
a reducing machine i6 illustrated in ~ig. 1. A frame-
work 1 is rotatably mounted about the longitudinal axis
of a log L. Multiple tool holders 2 are bolted to the
framework 1. Parallel guide rods or levers 3 are
pivotably mounted to the tool holders 2 and are in-
dependently attached to a milling tool 4 and its drivemotor 6 as shown. The other ends of the guide rod~
are attached to separate hydraulic actuators 7. The
hydraulic actuator~ 7 are mounted to the framework 1;
and, a skid-~haped headpiece or runner 5 i~ affixed
to the lead end of each milling tool 4.
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Adjustable guides 8 limit the swing of the
parallel guide rods 3 and are also mounted to portions
of the frame 1 as shown.
Sensing rollers 9 and 9' are suspended in-
dependently from the framework 1 by a means not shownand set at a distance from each other. The sensing
rollers 9 and ~' are positioned against the outer raw
surfaces of the log L and are connected electrically to
an electronic controller 10 which has transducers for
sensing the movements of the sensing rollers 9 and 9'.
The electronic controller 10 is electrically
connected to a conveying means, not shown, the rotating
means for the framework 1, the driving motors 6 and the
hydraulic actuators 7 for each of the reducing mach-
ine's reducing mechanisms.
The reducing machine has a conventionalfixed base, not shown, which rotatably supports the
framework 1 of the reducing mechanism. Conventional
conveyors (not shown) are positioned to feed raw logs
to the reducing machine and to receive the decorticated
or debasted logs from the reducing machine and trans-
port them to a sawmill (not shown).
In operation, a log L is fed to the reducing
machine at a uniform high rate of speed by the con-
ventional conveyor in the direction of the longitudinalaxis of the log.
As the log enters the reducing machine, the
sensing rollers 9 and 9' detect the exterior surface of
the rolled log and the electronic controller 10 signals
the hydraulic actuators to exert pressure on the par-
allel drive rods 3 to swing the milling tools 4 into
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contact with the head end of the log L. The millingtools 4 are swung in a plane containing the rotational
axis of the milling tools 4 and the longitudinal axis
of the log L. In moving the milling tools 4, the guide
rods 3 pivot about an axis perpendicular to the swing
plane of the milling tools 4.
The framework 1 is rotated about the log
causing the milling tools 4 to take a selected uni-
form depth of cut from the head end of the log. As the
log proceeds through the reducing machine, the runners
5 of the milling tools 4 are applied to the finished
log's outer surface which has been finished to the
selected depth. The cross-section defined by the
application-points of the runners 5 is designated as
the "reference cross-section" to which the remainder of
the raw log is then reduced.
When a predetermined amount of additional
pressure is required to be applied to the milling tool
4, the movement of the log is slowed by the controller
to compensate for the deeper cut, but ordinarily the
log proceeds through the machine at a constant speed.
In this respect, when changes in the cross-section of
the raw log are measured by the sensing rollers 9 and
9', they cause the electronic controller 10 to adjust
the feeding speed of the log as required. For example,
when higher gradients in the raw log's surface due to
large protuberances or root bulges are detected by the
sensing rollers 9 and 9', the feed speed is reduced by
the electronic controller 10.
During the debarking or debasting process,
the runners 5 of the milling tools 4 are constantly
positioned against the finished surface of the already
"reduced" log section, so that the entire length of the
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log is milled to a uniform cross-sectional shape and an excess
loss of wood is avoided.
In addition, the electronic controller 10 adjusts the
cutting depth of the milling tool 4 in response to the instan-
taneous gradients detected by sensing rollers 9 and 9'. The
cutting depth of the milling tool 4 is adjusted by the hydrau-
lic actuators 7 working together through the parallel guide arms
3 in the same forementioned swing plane in response to signals
from the electronic controller 10. Adjusting the cutting depth
of the tool 4 allows maintenance of a high feed-speed during
the debarking operation. The cutting depth of the milling tool
4, however, can be limited by setting the adjustable guides 8
which contact the guide arms 3 at the thusly adjusted limits
of the guide arm motion.
In another preferred embodiment, the swinging motion
of the milling tool 4 and the changes of its cutting depth may
be limited by means of positionable guides or by spring means.
Many modifications and variations of the present
invention are possible in light of the above teachings. For
example, the milling tool drive motors may be electric, hydrau-
lic or pneumatic. It is therefore to be understood that within
the scope of the appended claims the invention may be practiced
otherwise than as specifically described herein.
