Note: Descriptions are shown in the official language in which they were submitted.
~3~7
The present lnvention refers to an arran~ement with a tree relling
unit~ the cutting unit and grip arms of which are supported b~
a frame which is mounted at the end Or a crane boom or the like
and is tiltable laterally by means of at least a first hydraulic
member and tiltable in a forwards and backwards direction by at
least a second hydraulic member.
The fellin~ unit described above is used for cutting off tree
trunks adjacent the root portion and then transferring the cut~
o~f tree in an upright position for unloading or ~urther ~rocessing.
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In order to avoid the development o~ cracks in the root end of
the tree during the cuttin,~ operation, it is necessary that the
engage~en~ Or the grip arms be~ore the cutting operation is com-
pletely adapted to the tilt Or the grasped trunk portion without
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-biasing or inducing~tension in the crane boom supporting the
felling unit, transmitted to the whole vehicle, which in its turn
reacts on the tree. - This has~hitherto not been possible, as the
crane operator (bhe driver) from his seat has not been able;to
decide whether the tree is leaning somewhat towards him or aWay
from him, far less to decide ir prominences or other outgrowths
are present on~the back of the tree. The inavoidable ¢onsequence
is a positionin~, of the grip arms more or less at a random result-
ing in a biasing of the tree and~thus, in the felling (cutting)
operation, a crack.ing Or the root end and thereby a loss of the
most valuable wood. ~
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31L~3~727
This sincere drawback is eli~inated by the invention
by the fact that between the inlet and outlet conduits oE each
hydraulic member controlling the inclination of the frame is
inserted a control valve having a first and a second position
for closing and opening the path between the conduits, respect-
ively, there being means for after fixing and biasing actuation
of the grip arms around a tree, with said valve still in the
closing position but before actuation of the cutting unit,
momentaneously bringing the valve to its opening position, so -
that the biasing force of the tree is equalized and thus the -
frame is relieved from tension and accomodated to the grasped
trunk portion before the cutting action.
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An embodiment o~ the invention is described below
in conjunction with the accompanying drawing, the single
figure of which shows a schematic view of the inventional
arrangement. ;
In the following description of the invention, the
phantom lines indicate a part of a crane boom l, a generally
triangular support member 2, pivoted to the end of the boom and `~
supporting a frame 3 having an upper and a lower pair of grip
arms 4 and 5, respectively, and a cutting unit 6 immediately
below the lower grip arms unit. The gripping arms are operated
in the conventional way by actuating hydraulic cylinders 30 from
a hydraulic source 17 and the associated pump 16 via a three-way
valve 31, and the cutting unit 6 is operated, likewise in the
conventional manner, by actuating hydraulic cylinders 32 via a
two-way valve 33. A double-acting hydraulic cylinder 9 acting
between an ear 7 on the crane boom and an ear 8 on the support
2 is provided for controlling the tilt of the frame 3 in a for- ;
wards and backwards direction by means of a three-way valve 15a ~ -
connected to source 17. -
For the tilt of the frame in a lateral direction a
double-acting hydraulic cylinder 10 is used which is connected
t~
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between ears 11 on the ~rame 3 and ears 12 on the support 2,
whereby a tilting side~ays o~ the ~ra~e is accomplished by means
of a three-way val~e 15~, likewise connected to source 17
F~m, the t~o end ter~inals o~ the double-acting
hydraulic cylinder la inlet and outlet conduits 13 and 14 ,~
extend to said pump 16 and tank 17, respectively. Similarly, ~;
the cylinder 9 is connected to said pump and tank. ;
The invention resides in the ~act that the convention-
al conduits 13 and 14 ~and the corresponding conduits to ~ ~
cylinder 9) can be shunted ~y means of a special kind of a , ~' "'
two-way valvé 1~ via lines 19 and 20. In a first position
~the one shown) the valve maintains the lines 13 and 14
separated from each other ~the normal condition), but in its
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second position it connects said lines with each other via a ,",~
bridging path as sy~bolized by the right square in the figure. ''
In the latter position also a closed vessel 21 is utilized, t
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as described in the following. The valve position is control- ,~
led by an electrically operated control unit 22, as of an ~ -
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electric magnet type, against a return force, in this case
symbolized by a spring 23. The control unit 22 is supplied
from one contact 24 of a switching relay, having the general ,~
designation 25, the second contact 26 of which is connected
to an operation coil 27 of the magnet valve 33 for actuating ,~
the hydraulie eylinder 32 of the cutting unit in the assembly
6.
The electric components described above, inelusive ,
the coil 28 of the time relay 25, is provided with a positive
driving potential via a button operated switch 29.
The hydraulic cylinder 9 for controlling the
forwards and backwards tilt of the frame 3 has, like the
hydraulic cylinder 10, its inlet and outlet interconnectable ~ ,
by a two-way valve, possibly the same as that provided for the
hydraulic cylinder 10, and is operated through the same electric
A circuit 24-29.
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The operation of the arrangement described aboYe l ;
is as follo~s: ~-
~y coordinating o~ the hydraulic cylinders ~ and 10
by means o~ the corresponding three-way ~alves 15 in a right
and a left position, the driver ~operator) tries to move the
frame 3 with opened grip arm pairs 4 and 5 towards a selected
tree. As the next step, the driver switches the three-way
valve 15 to its neutral mid position (shown in the igure)
and provides full supply for the hydraulic cylinders 30
for the upper and lower grip arm pairs 4 and 5. These arm `
pairs then force the frame 3 to an optimal conformance to
the tree, whereby, however, the initially only approximate
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adaption results in forced strains in the crane arm 1. As
this arm of necessity must be extremely rigid as well as its !~
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anchoring in the supporting and substantially non-displaceable
vehicle, the tree itself will be subj~ected to the major part
of the strains. A cutting-off under these circumstances
would result in a cracking of the root end of the tree, as
already descrlbed.
However, the driver now pushes the button of the t
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switch 29. Hereby the coil 28 of the switching time relay
25 is energized and switches momentaneously its contact to
the position shown in the figure, i.e. against the contact
24, so that the control device 22 switches, against the force
of the spring 23, the two-way valve 18 from its blocking
position shown in the figure to the position symbolically
represented to the right in the figure; i.e. the shunt lines l- `;
19, 20 and thus the lines 13, 14 are bridged. (~he arrange- !"`
ment is similar as shown or common with the raising or lower~
ing hydraulic cylinder 9 indicated by the phantom rectangle
R). The fluid in the two cylinders 10 and 9 can now be
equalized under the action from the biased tree, the excess ; -
or deficiency of ~luid due to the different areas of the
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opposite faces o~ the piston i~ compensated b~ means o the
fluid vessel 21. All this normally takes place durin~ a
fraction of a second. The time relay 25 is chosen to have
such a time constant that it only alter the e~ualization o~
fluid switches over to the contact 25, where~y, on one hand,
the supply to the control device 22 is interrupted, and con-
sequently the valve 28 is returned by the spring 25 to the
blocking or rest position, and, on the other hand, the actuating
coil 27 for the magnet valve 33 for actuation of the hydraulic
cylinder 32 and, thus, advancing the cutting member against
the now unbiased tree is energized.
As is clear from the above the driver is not burdened ~;
with an extra manipulation; like the prior art he just presses -~
a button after forcing the grip arms around a tree.
It is also to be noted that the arrangement of the
invention reduces the duration of time for the breaking
strains of the crane
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boom to a small f'raction, as compared with prior art.
Various modirications are possible ~rithin the scope of the in- ~;
vention, especially by interchanging the described components
with equivalent units. '
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