Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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A device and a method for the netting of trees
The invention relates to a device and a method for the netting of trees as
featured in the preamble to claim 1 and claim 13.
Usually such devices comprise a supply opening that is configured at the end
of a funnel-shape tube being, at its opposite end, connected to a cylindrical
tube. The device is positioned horizontally, the tree to be netted being
pressed with its cut-off end first into the wide end of the funnel-shaped tube
1 o and continuing into the cylindrical tube. A gripper claw or hook can be
provided for pulling the tree through the cylindrical tube. A sleeving or hose-
shaped net has been pushed over the cylindrical tube, the end of the net
being suspended beyond the end thereof. When a tree is pushed through the
funnel-shaped tube with its cut-off end first, the free end of the net is
secured
to the tree - either by a knot being tied at the end of the net or by the net
being secured relative to the tree in any other manner, and the net is
subsequently pulled off the cylindrical tube as the tree is pulled there
through.
When the tree is pulled completely through the cylindrical tube, the net is
cut
off, which is preferably performed manually - and the tree is netted.
This prior art device for the netting of trees suffers from the overall
drawback
that the net around the netted trees is not very tight, it being effectively
wrapped around the tree only when the latter has left the cylindrical tube.
Hereby the branches of the tree are allowed to partially expand again prior to
2 5 being "caught" by the net. The fact that the net is not stretched to a
significant degree in its longitudinal direction either also contributes to
the not
very tight netting of the trees. Besides, slack netting also means that more
net than actually needed is consumed.
3 o Also, this device is associated with the drawback that - when used for
large
scale operation where a large number of trees are netted - three persons are
usually required to complete the operation: one for feeding trees to the
device, one for cutting off the sleeving, and. one for discharging the netted
trees from the device.
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Finally, this prior art device is fairly long, partly due to the protracted
length of
the funnel-shaped tube and the cylindrical tube, and partly because the trees
to be netted are pulled all the way through the funnel-shaped tube by means
of a pulling device. The friction that occurs between the tree to be netted
and
the inside of the cylindrical tube is also of a significant magnitude, in
particular when the cylindrical tube is long as is the case with the prior art
device.
1 o It is the object of the present invention to provide a device and a method
for
the netting of trees, said device and said method overcoming the above-
described drawbacks of the prior art.
This is accomplished by configuring the device featured in the preamble to
claim 1 as featured in the characterising part of claim 1.
Besides it is accomplished by the method featured in the preamble to claim
13 further featuring the step described in the characterising part of claim
13.
2 o Hereby it is obtained primarily that the net around the trees becomes
considerably tighter than was the case with the prior art devices where the
net is not applied until the tree leaves the cylindrical tube. This is
obtained
partly by the net being applied within the netting tube while the tree is
completely compressed, and partly by the net being stretched in its
longitudinal direction when pulled beyond the edge of the netting tube and
through it. By tightening the net in this manner a reduced net consumption is
also obtained. Finally the friction between the tree and the inside of the
netting tube is reduced compared to the prior art, the net located between the
tree and the netting tube servicing as an anti-friction layer.
The dependent claims feature particularly preferred embodiments that further
improve the device according to the invention.
The invention will now be described with reference to the drawing, wherein
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Figure- 1 is an explanatory sketch showing a device for the netting of trees
according to the invention;
Figure 2 shows an explanatory cross section of the device; and
Figure 3 shows a tree partially pulled through the device shown in Figures 1
and 2.
1 o As will appear from Figures 1 and 2, a preferred explanatory embodiment of
a device for the netting of trees in accordance with the invention comprises a
supply opening 1 provided, in the embodiment shown, in a plate 2 in the form
of a circular opening having an inclined edge 3, whereby the supply opening
1 is caused to have a larger diameter on the forwardly oriented side of the
plate 2 than on the opposite side.
Immediately behind the supply opening 1 and at a short distance therefrom, a
netting tube 4 is provided that consists of a circular tube having an internal
diameter that corresponds essentially to the smallest diameter of the supply
2 0 opening 1, ie corresponds to the dimension of the supply opening 1 in the
plate 2 at the side that faces towards the netting tube 4. At the outside, the
netting tube 4 is provided with a sleeve- or hose-shaped net 5 that is
compressed in the longitudinal direction, as shown, which means that - as a
starting point - it fills the netting tube 4 along the entire longitudinal
expanse
thereof. Such compression of the net 5 enables positioning of many metres
of net sleeving 5 on the comparatively short netting tube 4.
At the rear end the netting tube 4 is provided with a flange 6 that
constitutes
an end stop for the net 5, whereby it is kept on the netting tube 4. At the
front
3 o end the end stop of the net 5 is constituted by the plate 2 with the
supply
opening 1, the plate 2 being, however, located a short distance from the
netting tube 4 to allow the net 5 to be pulled around the front end 7 of the
netting tube 4, whereby this end of the net 5 can be bent into the netting
tube
4, as shown in Figure 2. The distance between the front edge 7 of the netting
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tube 4 and the plate 2 has exactly such expanse that there is room for the net
to be located there between. If a-commonly used net 5 of nylon is used, the
distance between the netting tube 4 and the plate 2 needs only be about 1
mm.
5
According to a preferred embodiment the netting tube 4 is, at the front edge 7
provided with an outwardly protruding bead 8 that causes the net 5 to be
stretched when it is pulled across the bead 8. Hereby a further tightening of
the net 5 is obtained when it is pulled through the netting tube 4, as will be
1 o described below.
A pull device is provided for pulling a tree to be netted through the supply
opening 1 and the netting tube 4. The pulling device comprises two gripper
claws 9, each of which being securely attached to a rotatable tube 10 via a
lever 11. On each lever 11 a pull bar 12 is pivotally mounted that is, at its
opposite end, connected to a hydraulic cylinder 13 via a connector element
14. When the hydraulic cylinder 13 is activated, this construction causes the
gripper claws 9 to first be pulled towards each other, optionally around the
cut-off end of a tree, following which the entire pull device will be
displaced to
2 o the right in Figures 1 and 2.
A cutter device 15 is provided immediately after the netting tube 4, said
cutter
device 15 comprising, in the embodiment shown, two rotatably mounted and
partially overlapping cutter blades 16 that efficiently cut the net 5 off when
they are conveyed downwards through an empty net 5 after a tree has been
pulled through the device. Underneath the cutter blades 16, two conical
rollers 17,18 are mounted that have between them a narrow slot. These
rollers 17,18 rest against the netted tree as it leaves the netting tube 4,
and
the moment the top of the tree has travelled past the rollers and there
remains only net 5, the cutter device drops downwards due to its weight, the
net 5 penetrating upwards between the rollers 17 and 18, and the cutter
blades 16 cutting off the net 5.
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Preferably the cutter device is rotatably mounted about an axis parallel with
the longitudinal axis of the netting tube, which is not, however, shown in
further detail.
5 A cutter device configured in this manner is of course not restricted to use
in
connection with a device for the netting of trees according to the present
invention, but it may just as well be useful in connection with other devices
for the netting of trees.
l o Finally, a conveyor belt 19 is provided that is able to transport the
netted tree
away from the netting device as such.
In the starting position the device for the netting of trees is adjusted as
shown
in Figure 2, ie with the front end of the net 5 within the netting tube 4 and
the
gripper jaws 9 also within the netting tube 4, they being preferably located
at
the inner face thereof. The cut-off end of a tree to be netted is now conveyed
into the supply opening 1 and further into the netting tube 4, where it is
enclosed by the net 5, whose end is loosely suspended within the netting
tube 4. Then the hydraulic cylinder 13 is activated whereby the gripper jaws 9
2 o are caused to engage with the cut-ofF end of the tree as explained above.
When the gripper jaws 9 encounter sufficient resistance to further penetration
into the cut-off end, the continued pull of the hydraulic cylinder 13 causes
the
tree to be pulled through the supply opening 1 and further through the netting
tube 4, while the net 5 is pulled along between the tree and the inner face of
the netting tube 4. This stage of the netting procedure is shown schematically
in Figure 3.
The pull device is able to pull the entire tree through the netting tube 4,
but
preferably the pull device stops when the thickest portion of the tree has
3 o been pulled through, since it is possible to pull the remainder of the
tree
through by use of less force. Hereby the device according to the invention
can be made significantly shorter than the known devices where a pull device
pulls the entire tree through the funnel-shaped tube and the cylindrical tube.
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When the thickest portion of the tree has been pulled through the netting tube
4, the netted portion drops onto the conveyor belt 19 that contributes with
sufficient force to pull the remainder of the tree through the netting tube 4.
If it
is a case of particularly thick trees that yield extra resistance to being
pulled
through, a second conveyor belt may be provided above the conveyor belt
19, whereby it is possible to sandwich the tree between the two conveyor
belts, thereby generating more friction between the conveyor belts and the
tree. This additional conveyor belt may be vertically displaceable, which
means that it is able to engage with trees of varying thicknesses.
Preferably, the rate of the conveyor belt 19 corresponds to the rate of the
pull
device whereby the conveyor belt 19 cooperates with the pull device when
the tree drops thereon. However, the conveyor belt 19 may be configured
such that it runs at an increased rate, eg 2.5 times faster, when the pull
device has let go of the cut-off end of the tree and is moved back to its
starting position, whereby the tree is removed from the netting tube 4 more
quickly.
As mentioned previously the netting tube 4 is, in the preferred embodiment,
2 o provided, at the front edge 7, with an outwardly protruding bead 8 that
causes the net 5 to be stretched when pulled across the bead 8. Preferably
the bead 8 has an outer diameter that corresponds essentially to the
maximum diameter of the net sleeving 5, whereby additional resistance
against the net 5 being pulled over the edge 7 is generated, with the result
that the net 5 within the netting tube 4 is further tightened in the
longitudinal
direction when a tree along with the net 5 is pulled through the netting tube
4.
Hereby tight netting of the tree is accomplished.
The shown and described device for the netting of trees is provided with a
3o hydraulic pull device for pulling trees through the device. However, there
is
nothing to prevent the use of other kinds of pull devices, eg a mechanical
device, or to altogether omit same and pull the trees through the device
manually.
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The shown and described device can be constructed as a separate unit or it
may be constructed for mounting on eg a tractor or other forestry machinery.
Likewise, it may be combined with other units, such as eg a palleting unit to
which the conveyor belt may convey the netted trees.
Finally the netting tube can be configured as a replaceable cassette, which
means that it can readily be replaced when the net on the first netting tube
has been used up. Optionally, a winding device can be mounted instead of
the netting tube, whereby the same device can also be used for tying trees.
