Note: Descriptions are shown in the official language in which they were submitted.
WO 8~/05062 Our Ref: 014150-021
PCT/EP85/00186
Sawing and Cutting Apparatus for Logs
The invention relates to a sawing and cu-tting apparatus for logs,
with at least one knife head which serves as a cutting tool for
the production of wood chips and at least one circular sawblade
connected with a saw shaft arranged coaxially and spaced thereto
which serves -to saw off at least one sideboard.
In the processing of round -timber logs to lumber such as boards
and square timber, it is known from tha so-called profile-cutting
method how to cut the exterior wood parts which would give slabs
with knife heads to wood chips suitable, for example, for the
production of chipboard or cellulose.
In a known apparatus of the initially described type (DE-OS 29 47 190),
two opposite-lying knife heads and several intermediate-lying
circular saw blades are arranged on a common shaft. The difficulty
with this, howe~er, is that the knife heads have to be driven at a
relatively low rotational speed to produce wood chips of suff'icient
fiber length, whereas a suf'ficiently high rotational speed is
required for driving the circular sawblade with respect to the
required sawing quality. Both requirements can no-t be fulfilled
simultaneously with the known apparatus, so that in general a too
high rotational speed of the knife heads and with it an insufficien-t
quality of the wood chips produced has to be put up wi-th.
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Furthermore, in the known apparatus the circular sawblades are
arranged rigidly on the common drive shaft so that only boards
or square timber of constant width can be produced. An adjust-
ment to different desired dimensions is not possible or only
through an expensive reconstruction of the apparatus.
It has already been known for a long time (DE-OS 20 10 o60) how
to carry out the sawing process for the production of the side-
board or sideboards simultaneously, but independent of the cutting
process. In the known apparatus, belt saws or gang saws are used
which also make possible an adjustment of the width. The feed rate
of the logs must be chosen relatively low in this case, however,
to accomodate the requirements of the sawblades, which in turn is
disadvantageous for the cutting process.
The relatively high feed rate of the logs possible with the cutting
-tools for wood chip produc-tion, which is desirable for reasons of
high work capacity, makes it necessary to carry out the sawing-off
of the sideboard or sideboards, respectively, with rapidly running
circular saws which are usually spaced at greater distances to the
cutting tools in the feed direc-tion of the logs, for example, double
circular saws in pairs on -top of each other, or displaced with
respect to one another. In this arrangement, with a high feed rate,
the rota-tional speeds of the knife heads and circular sawblades can
be optimally chosen in each instance wi-th a high feed rate of the
logs, but the spatial separation of the knife heads and the circular
sawblades causes unavoidable imprecisions, especially for the
-thickness of the sideboard to be sawed off. Only with expensive
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guide measures can i-t be assured that the surface of the sideboard
sawed by the circular sawblades is sufficiently parallel to the plane
surface produced beforehand by the knife head (DE-OS 29 18 622).
It is therefore the object of the inven-tion -to design a sawing and
cutting apparatus of the initially described type in such a way that
an adjustment to varying thicknesses of the sideboard to be sawed off
is made possible at optimal speeds of the knife head and the circular
sawblade in a straightforward manner.
This object is attained according to the invention by connecting
the knife head with a hollow shaft, supporting the saw shaft
rotatably and axially displaceable in the hollow shaft and connecting
the saw shaft with a drive apparatus which delivers a higher rota-
tional speed than the hollow shaft.
With the separa-te drive of the saw shaft with higher rota-tional
speeds than the hollow shaft of the knife head, the respective
optimal rotational speeds can be chosen for each of the two
separate working processes, so that on the one hand wood chips
with sufficiently large fiber length are produced at a high feed
rate of the logs, and on the other hand a high work quality of
the saw cutting is achieved. Because the cutting process which
also delivers the outer plane surface is carried out simultaneously
with the sawing process and in close spatial proximity thereto, it
is assured that the two lateral faces of the sideboard produced in
in this way and the thickness of the sideboard remain constant.
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These conditions remain the same when -the circular sawblades are
adjusted -to change the thickness of the sideboard which is made
possible in a very simple way by axial displacement of the saw
shaft in the hollow shaft.
If the application field of the apparatus according to the invention
was stated before as the processing of logs, the processing of round
timber logs on two opposite sides is to be understood hereunder, and
also the processing of modules which were already flattened on two
sides and then processed on sides lying opposite to one ano-ther.
It is known however (DE-PS 21 ~8 912) how to attach a knife head to a
hollow shaft for profile cutting of the lateral face of a log in which
a faster running saw shaft is supported which carries a circular saw-
blade. Herein, however, the circular sawblade is situated in the
front side of the knlfe head and does not serve to saw off a side-
board, but only to smooth the surface produced by the knife head.
An axial displacement of the circular sawblade is not provided for
and would not make sense here.
Axially displaceable circular saws arranged on coaxial hollow shafts
are known in di~ferent embodiments (US-PS 3 630 2L~L~). These known
apparatus only serve for the transverse adjus-tment of the circular
sawblades, however; they do no-t have knife heads as cutting tools.
The thus adjustable circular sawblades are driven by a common drive
at the same rotational speed.
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In a further development of the inven~ion, it is
provided that the flight diameter of the circular sawblade is at
most two times the wood chip length smaller than the flight
diameter of the closest-lying cutting edges of the knife head. In
this ~7ay, it is accomplished that at the end of a log the cutting
process of the knife head is finished before the sawing process is
finished.
In order to achieve a simple and especially compact
construction, it is advantageously provided that the hollow shaft
and the saw shaft are connected with a common drive motor via two
gear trains with different transmission ratios.
It is known,however, (DE-A-33 12 033, Fig. 13) how to
arrange an axially displaceable, separately driven circular saw
blade with axial spacing in front of a knife head. The saw shaft
which carries this circular saw blade is not however supported in
the hollow shat connected with the knife head and is not coa~ial
to it, but rather it is supported in a rigid bearing body lying in
the interior of the hollow shaft, whereby the bearing of the saw
shaft lies eccentrically to the hollow shaft carrying the knife
head.
This known apparatus is of relatively complicated make,
because on the one hand a bearing of the hollow shaft carrying the
knife head on the rigid bearing body and on the other hand a
bearing of the saw shaft carrying the circular sawblade in this
rigid bearing body are required.
Also, the circular sawblade which is frontally attached
to the knife head is missing in this known device. The sa~ed-off
sideboard does not show a sawed surface on lts exterior but rather
a surface produced by the knife head which can have fissures and
the like.
On the front side of the knife head facing the circular
sawblade another circular sawblade can be attached which smooths
the outer surface of the sideboard in a way known per se r and
avoids roughness and flssures from the cutting process.
To process opposite sides of a log one knlfe head can be
provided on each side of the log which has an axially adjustable
circular sawblade. In order to make possible a quick and simple
adjustment to different dimensions of the log, a sled carrying the
bearing of the hollow shaft can be guided in a machine frame and
adjusted transversely with respect to the transportation
direction .
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The invention is explained in more detail with respect to an em-
bodiment shown in the drawing.
Fig. 1 shows a sawing and cutting apparatus for logs in a partial
cross-section, and
Fig. 2 is a lateral view in the direction of the arrow II in Fig. 1.
The sawing and cutting apparatus shown in the drawing serves in -the
embodiment shown to process the opposite sides of a module 1, the
upper side and under side of which have already been flattened.
The module 1 which is designa-ted in general in the following as a
log is guided by a feed and transportation apparatus of which only
a transportation roller 2 is shown in Fig. 2 over a support 3. On
both sides of the support 3, a knife head 4 equipped with chopping
knives is arranged which serves to cut up the lateral parts la of
the log 1 into wood chips.
The knife head 4 is attached to a hollow shaft 5 which is pivoted
in a sled 7 with bearings 6. The sled 7 is displaceably guided on
guideways 8 transversely to the transportation direction of the log 1.
In the hollow shaft 5 of the knife head 4 a saw shaft 10 is pivo-ted
and axially displaceably supported on bearings 9. The saw shaft 10
carries a circular sawblade 11 on its free end which serves to saw
off a sideboard lb from the log 1. On the front side facing the
circular sawblade 11 a further circular sawblade 12 is attached on
the knife head 4 which serves to smoo-th the outer surface of the side-
board lb.
_ 9 _
At the end of the hollow shaft 5 a belt pulley 13 is attached which
is connected over a belt drive 14 wi-th a bslt pulley 15 on the
output shaft of a drive motor 16 which is supported by the sled 7.
A belt pulley 17 with a diameter which is smaller than that of the
belt pulley 13 is pivoted at the back end of the hollow shaft 5
with a bearing 18 and forms a drive connection with the saw shaft 1
over an adjusting spring 9, whereby howsver an axial relative move-
ment is possible. The belt pulley 17 is connected with a belt
pulley 21 on the output shaft of the drive motor 16 over a belt
drive 20. The diameter of the belt pulley 21 is larger than that
of the belt pulley 15.
With the described choice of diameters of the belt pulleys 13,15,17
and 21, it is accomplished that the saw shaft 10 is driven at a
higher rotational speed than the hollow shaft 5 by the common drive
motor 16. The saw shaft 10 receives a relatively high speed required
for an optimal sawing process of the circular sawblade 11, whereas
the knife head L~ is driven with the relatively low rotational speed
which is optimal for the production of wood chips.
The drive and -the adjustment of the circular sawblade lL~ on the
opposite side of the log 1 and of the knife head 4 is carried out
in the same manner as described; the apparatus used herefor which
was built in the manner described was therefore left out of Fig. 1.
In the embodiment shown, the flight diameter of the circular saw-
blade 11 is approximately equal to the flight diameter of the knife
head 4 or the circular sawblade 12 attached to i-t, respectively.
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On the right hand side of the log 1 it is shown on the circular
sawblade 11 that its flight diameter can also be chosen smaller
than the assigned knife head 4, so tha-t the circular sawblade 11
still cuts when the knife head 4 or the attached circular saw-
blade, respectively, is already out o~ engagement wi-th the wood.
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