Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1285291
The present invention relates to a process for feeding
tree trunks to a processing machine by means of centering
elements, each of which can be adjusted to be arranged
symmetrically to the centre line of the processing machine,
a plurality of guide surfaces that are opposite each other
being milled on the trunk before it enters the processing
machinery, these then immediately engaging with guide
elements.
Tree trunks that are to be processed into beams, s~uare
lumber, boards and, in some cases, into usable chips and
shavings, in processing machinery such as sawmills and
shaping machinery, must be fed into said processing
machinery in a straight line, such that the centre line of
the feed path coincides precisely with the centre line of
the tree trunk, so as to permit optimum utilization of the
wood. Any oscillation of the tree trunk has to be prevented
as far as possible, for otherwise the cuts are not made in
an accurate, straight line.
In order to permit such precise, rectilinear feeding of
tree trunks into a processing machine, it is known that
guide surfaces can first be milled on the tree trunk; these
guide surfaces are rectilinear and make it possible to guide
the tree trunk in a straight line along such surfaces as it
is being fed into the machinery. This means that the
difficulties that result from using the conical and usually
curved shape of the outer surface of the tree trunks as
guide surfaces can be overcome in the immediate vicinity of
the processing machinery; in actual fact, this difficulties
are only set aside, for the tree trunk must be guided in a
straight line in alignment with the centre axis of the tree
trunk in order to mill the guide surfaces.
In a known process (DE-PS 29 21 458), in order that
this can be done the tree trunks are picked up in the
central area and at the ends by centrally positionable
grippers, each of which is supported on a slide that can be
moved along a rail. The tree trunks that have been so
picked up are moved to milling machines that mill the
processing surfaces on which the tree trunks are then guided
by means of guide rollers. As soon as the start of the tree
trunk i8 picked up by these rollers, the centre gripper
opens; the tree trunk is then guided between the guide
rollers and the rear gripper. The trunk that is so guided
and partially processed is passed to a processing system in
which the tree trunk is milled to a cylindrical shape.
There is a further support on this cylindrical surface,
while the tree trunk, processed on all sides, is passed to a
plurality of feed rollers that are arranged at the input to
a subsequent processing machine, such as a saw, for example.
The installation required for this known process is
relatively complex. The slides that bear the grippers and
which can be moved along the rails have to be returned to
their starting positions once a tree trunk has passed and
then be loaded before they can move the next tree trunk into
the system. This means that that very close limits are
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imposed on the operating rates that can be achieved. Using
the known process, in order to permit precise guidance of
the tree trunk at the intake of the processing machinery two
guide surfaces must be milled on one after the other in two
processing stages, which is to say, one for the initial
guidance of the start of the trunk, and the other to achieve
the cylindrical outer surface prior to entering the group of
guide rollers at the start of the processing machinery.
For this reason, it is the task of the present
invention to create a process of the type described in the
introduction hereto and which permits a rapid operating
cycle and precise feeding of the tree trunks into a
processing machine at very little cost and in a
labour-saving manner.
In addtion, the present invention is intended to create
an apparatus that is suitable for carrying out the aforesaid
process.
According to the present invention, this task has been
solved in tht a plurality of groups of centering rollers--at
least some of which can be driven--arranged sequentially in
the direction in which the tree trunks are moved are so
controlled when a tree trunk is fed in that the centering
rollers of the groups through which the start and the end of
the trunk is moving are adjusted symmetrically, whereas the
centering rollers of the remaining groups remain in their
withdrawn or unloaded position, respectively.
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In contrast to the grippers that move with the tree
trunk, in the process according to the present invention the
individual groups of centering rollers remain fixed in
place. The only locations that move forward with the tree
trunk are those at which the centering rollers support the
tree trunk symmetrically to its centre line. This support
is effective at the ends of the tree trunk during the whole
of the feed process, i.e., all the groups of centering
rollers through which the end of the trunk moves in sequence
guide and support the end of the trunk. The front of the
trunk is supported and guided by the group of centering
rollers through which it is passing only until it is
introduced into the machine that mills on the guide
surfaces, which are then supported immediately afterwards by
the guide elements.
In this feed movement the tree trunk can be fed to the
processing machinery, for example, a saw, immediately
afterwards, without any need to support it between guide
rollers. The whole operating cycle can be continuous, for
the start of a subsequent trunk can abut directly on the end
of a preceding trunk. This permits very high operating
speeds.
It is known that in order to feed tree trunks to
processing machinery, centering rollers that can be
positioned centrally from opposite sides (DE-OS 16 28 866).
Here, however, the centering rollers are arranged in two
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fixed groups through which the trunk moves. If the trunk is
curved, it will oscillate.
It is also known to use a roller bed in feed systems for
wood processing machinery, said bed supporting the tree trunk (DE-
OS 32 46 969). Here, however, the tree trunk is guided along its
lower surface line, so that in general it is impossible to align
lt centrally with the centre feed line of the processing
machinery.
According to a broad aspect of the invention there is
provlded, in a process of feeding tree trunks to a processing
machlne, the process including the step of cutting guide surfaces
into the tree trunk at a cutting station disposed upstream of the
processing machlne whereafter the guide surfaces are engaged and
supported by guide elements disposed between the cutting station
and the processing machine, the improvement comprising centering
the tree trunk along a centering line of the processing machine
during the delivery of a tree trunk to the cutting station by the
steps of:
providing groups of centering rolls upstream of said cutting
station, said groups being spaced along said centering line,
centering rolls of each said group being adjustable symmetrically
between trunk centering and trunk non-centering modes, at least
some of said centering rolls being driven to advance a tree trunk,
and
advancing the tree trunk along said centering line
successively through said groups of centering rolls while
successively adjusting said groups between their centering ar;d
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non-centering modes such that groups thereof located to support
front and rear ends of the advancing tree trunk are in their
centering modes while at least one group disposed therebetween is
in a non-centering mode.
According to another broad aspect of the invention there
is provided apparatus for processing tree trunks comprising a
processing machine defining a centering line, cutting means
disposed upstream of said processing machine for cutting guide
surfaces into a tree trunk, guide elements disposed between said
cuttlng means and said processing machine for engaging and
supporting the guide surfaces durlng travel of a tree trunk to
said processing machine, the improvement comprising centering
means for centering a tree trunk along said centering line during
the delivery of the tree trunk to said cutting means, said
centering means comprising:
groups of centering rolls disposed upstream of said cutting
means, said groups being spaced along said centering line,
centering rolls of each sald group being adjustable symmetrically
between trunk centerlng and trunk non-centering modes,
means for driving at least some of said centerlng rolls for
advancing a tree trunk successively through said groups of
centering rolls, and means for successively adjusting said groups
between thelr centerlng and non-centering modes such that groups
~: thereof arranged to support front and rear ends of the advancing
tree trunk are in their centering modes while at least one group
: disposed therebetween is in a non-centering mode.
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An advantageous systeln ~or carrying out the process is
described in greater detail below on the basis of the drawings
appended hereto. These drawings are as follows:
Figure 1: A side view of an apparatus for feeding tree
trunks to a saw;
Figures 2 to 4: The apparatus as in Figure 1, in
sequential steps of the feed process;
Figure 5, An enlarged partial cross-section on the line
V-V in Figure 4;
Figure 6: A partial view in the direction indicated by
the arrow VI in Figure 5.
The feed apparatus shown in the drawings has a chain bed
2 ~hat can be raised by means of the parallel arms 1 and can
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be driven, the tree trunk 3 that is to be processed is moved
on this chain bed 2. Above the exit end of the chain bed 2
there is a follower roller 4 that is so arranged that it can
move vertically; this roller is connected to a measuring
system (not shown herein). As soon as a tree trunk 3 lies
in the position on the chain bed 2 that is shown in Figure 1
it is raised until a signal that is emitted from the
follower roller 4 indicates that the centre of the tree
trunk 2 is close to the centre feed line. The chain bed 2
is fixed at this level, while the tree trunk 3 is moved
ahead. As is shown in Figure 2, the tree trunk 3 passes
through a plurality of groups 5 - 10 of centering rollers 11
arranged in sequence one after the other, each of which can
be arranged symmterically to the centre feed line 12.
Figure 5 shows that each group 5 - 10 of centering
rollers 11 is has two centering roller 11 pairs that are
opposite. The centering rollers 11 that can be driven
individually from the drive motors 13 are in each instance
supported on a pivot arm 14 arranged in turn on a pivot
shaft 15. In each instance, the pivot arms 15 of the
centering rollers 11 that are opposite each other are
connected to each other through crank arms 16 and a common
arm 17. A pressure operated cylinder 18 drives the
centering rollers 11 that are so connected and opposite to
each other to opposing adjusting movements symmetrically to
the centre feed line 12 (Figure 6).
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A control system (now shown herein) receives a signal
that indicates the position of the start and the end of the
trunk. This signal can, for example, be sent from a
plurality of light barriers (not shown herein) arranged
alson the path followed by the tree trunks. In place of
this, it is also possible to determine the positions of the
start and the end of the tree trunk by computer, once the
initial position of the tree trunk 3 has been determined.
The control system controls the cylinder 18 for the
positioning movement of the centering rollers in such a
manner that each centering roller 11 of the group 5 to 10
that i8 located at the start and the end of the trunk is
moved into position, whereas the remaining centering rollers
11 are in the position in which they are withdrawn and not
on contact with the tree trunk.
Thus, one can see that in Figure 2 the centering rollrs
11 of group 8 are in position on the start of the tree
trunk. In addition, the centering rollers of group 10 are
still in position; they are guiding the end of the preceding
trunk. The centering rollers of group 5 are still
positioned because they are taking over the tree trunk 3
from the chain bed 2.
In the position that is shown in Figure 2, the tree
trunk 3 is between the centering rollers 11 of the forward
group 10 at the start of the tree trunk and between the
centering rollers 11 of the rearmost group 5 at the end of
the trunk. In this position, the tree trunk moves into a
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processing station 19, within which a plurality of milling
heads 20 that are located opposite each other mill opposing
guide surfaces 21 on the tree trunk 3 (Figure 4).
Immediately after passing through the milling heads 20 these
guide surfaces 21 are supported and guided on the guide
bodies 22.
Immediately after this, the tree trunk 3 enters a
processing machine 23 which, in the embodiment shown
incorporates a group of circular saws 24, by means of which
the tree trunk is cut intD;square timbers or boards. Whilst
the tree trunk is moving through the processing machine 23,
immediately prior to this it is guided by the guide bodies
22 and at its trunk end by the centering rollers that are
positioned there.
The milling heads 20 can be so arranged and designed
that they mill four lengthwise edges on the tree trunk 3,
these serving as guide surfaces for the subsequent guide
bodies 22 and at the same time form the edges of the side
boards in the subseguent sawing process.
As can be seen from the drawing, the tree trunk 3 is
moved into position root-end first. The top end that forms
the rear end of the trunk is, in most cases, straight,
whereas the root end is very often curved on one side.
Thus, the tree trunk 3 is centred at the straight top end,
while the preceding root end has had its sides milled by the
milling heads 20 at the start of the feed process.
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The guide bodies 22 can be replaced by guide rollers if
the forces that are generated by the subsequent processing
machinery are almost balanced out. In the case of greater
processing forces that act on one side, the guide bodies 22
are more suitable for guidance and for providing lateral
support.
In the description of the embodiment it was stated that
the centering rollers 11 that carry out no guiding function
for the tree trunk 3 are withdrawn. In place of this, it
can be arranged that these centering rollers are only
unloaded; the centering rollers then still rest on the tree
trunk 3, although they exert no significant lateral forces
on the tree trunk and for this reason fulfill no guiding
function.
In place of the arrangement shown for the present
embodiment, of four centering rollers 11 in each of the
groups 5 to 10, another number of centering rollers 11 can
be selected, for example, three centering rollers 11 spaced
at equal intervals about the periphery of the tree trunk.
It is also possible to provide for centering in one plane
only, preferably in the horizontal plane, there being in
each group 5 to 10 only two opposing centering rollers 11,
while the tree trunk 3 lies and is transported on a roller
bed, a chain bed, or on a similar horizontal guide surface.
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