Note: Descriptions are shown in the official language in which they were submitted.
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An Operating System for a Tree Harvester
Technical Field
The present inven-tion relates to an operating system for
a tree harvester, specifically a grapple processor. The operating
system is used for controlling and operating the hydraulic motors
of the tree feeder and the crosscut saw and further the hydraulic
cylinders required by the operation of the feeder and the limbing
blades.
State of the Art
Previously the control and operating valves in a
processor were placed in the power take-off machine itself. In
such a case, separate hydraulic lines for all functions were
directed via the loading jibs. But in such a case at least six
hydraulic lines from the basic machine to the processor are
required. Thus a tree harvester, intended as an accessory, was
not easy to install even in terms of the lines alone, not to speak
of the installation of many new additional valves in the power
take-off machine.
Nowadays the aim is to place the processor control
valves in the processor itself, but it is necessary to use
large-sized valve groups for the control of the necessary
hydraulic operations. This for its part increases the weight of
the equipment and requires several electrical cables between the
power take-off machine and the tree harvester.
Furthermore, these control valves implemented using
conventional technology usually require a constant-pressure pump,
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and soft control of these valves wil:h so-called on-off valves is
not possible. Likewise, it is difficult to place in the driver's
cabin of the power take-off machine -the control levers required by
the plurality of functions.
In grapple processors, hydraullcs is required during the
limbing movement, i.e. the feeding of the tree, for the crosscut
saw, and also for pressing the rolls or rollers of the feeder
against the tree. In general, the operating movements of the
limbing blades are also in the same circuit, i.e. when the feeder
is pressed against the tree also the limbing blades move towards
the tree. In several grapple processors these have a common
double-acting hydraulic cylinder.
Technical Problem and Its Solution
A grapple processor thus requires at least one hydraulic
motor for the feeding of the tree. This motor must be able to
rotate in both directions. Furthermore, the crosscut saw requires
pressurized oil in order to rotate in one direction. This opera-
tion takes place always at a time different from the time of the
feeding in of the tree. Thus, for gripping the tree and for the
limbing blades at least one double-acting hydraulic cylinder is
required. By means of this cylinder the pulling rolls and the
limbing blades are pressed against the tree. The feeding of the
tree and the crosscut saw require pressurized oil about 150 l/min,
whereas the cylinder of the feeder and the limbing blades requires
only about 30 l/min for the on-off action. During limbing, as the
diameter of the tree varies the cylinder needs pressurized oil
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only to keep -the feeder rolls and the limbing blades pressed
against the tree, the pressurized-oil requirement being only about
10 l/min.
The present invention provides an electro~ydraulic
operating sys-tem for a tree harvester, said sys-tem comprising: a
first and a second pressure oil line, each one capable of serving
as a feed line and, alternatively, as a return line, so as to
provide for the flow of oil in one or the other direction through
said system; a first motor for a tree-feeding device, said motor
being of a reversible type and connected between the first and
second pressure oil lines; a second motor for a cutting saw, said
motor being of one-directional type and connected between said
first and second pressure oil lines; power cylinder means for
effecting gripping of the tree during ~eeding and cutting opera-
tions; first valve means coupled in series with the first motor;
second valve means coupled in series with the second motor; ~Eirst
control means for opening of said fir~t and second va:Lve means
aLternatively and for preventing simultaneous opening to the first
and second va.Lve means; and second control means for operating
said power cylinder means and for inhibiting operation of the
first control means until the power cylinder means has reached a
tree-gripping position.
In the operating system according to the invention,
advantage is taken of the unidirectional pressurized-oil require-
ment of the saw motor, whereupon all the functions of the grapple
processor can be realized simply by utilizing the reversing valve
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in the power take-oEf machine. This valve may be, for example the
on-off direction control valve of the timber grapple, the valve
becoming free when the grapple is replaced by a processor. In
this case the controlling of the entire processor requires only
two pressurized-oil lines dimensioned for actual power trans-
mission between the power take-off machine and the processor. A
third line is required for the return oils of the control valves
and the feeder and the limbing blades. Ln this line the flow
volume is low. Furthermore, two separate electromechanical small
direction-control valves are required; one controls the pressure
of the pulling rolls and the limbing blades and the other controls
the on-off valves oE the tree feeder motors and the saw motor.
Two electrical cables between the power take-off machine and the
processor suffice for the control of these electromechanical
direction-control valves, since the metal Erame structures can
serve as the grouncling wire.
Uy adclincJ only two small e;l~etric switches in conjunc-
tion witll the on-oE dir~ctlon-cc~lltrol valve oE the timber grapple
in thc ~owe~r take-oEE maclline and by adding between the power
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take-off machine and the processor one return-oil line, described
above, in addition to the two electrical cables, most power take-
off machines can be used as the power take-off machine for the
grapple processor, without any other changes in the hydraulics.
The valves placed in the processor part may all be so-called on-
off valves, since the speed of the operations is controlled by
means of the direction-control valve in the power take-off
machine.
Drawing
The accompanying drawing depicts diagrammatically the
operating system according to the invention.
Preferred Embodiment
As is evident from the figure, hydraulic-oil lines 2 and
3 and return-oil Jine 4 lead from the power take-off machine to
the tree harvester 1. Line 2 connects valves 8 and 10. Line 3
connects valves 7 and 9. Line 4 connects the return lines of
valves 14 and lS. T.ine 13 connects valves 14 and ll and 20.
Working pressure from llne 2 or 3 acts on line 13 by transmission
of valves 7, 8, 1l and 12.
From valve 14, control pressurized-oil line 19 leads to
valves 7, 8 and 9 (dashed lines). The tree-feeder motor 5 is
between valves 7 and 8. The crosscut-saw motor 6 is between
valves 9 and 10. The operating cylinder 18 of the feeder and the
limbing blades is connected to valve 15 by means of lines 17 and
16. Valves 7 and 8 are preferably counterbalance valves which can
be opened by the control pressure. Valve 9 for its part can
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preferably be closed by the control pressure, e.g. a seat valve,
i.e. through-flow of valve 9 is possible when the control pressure
is not effective in line 19.
Valves 10, 11 and 12 are ordinary counterbalance valves.
Valves 14 and 15 are electromechanical 2-position direction-
control valves. Between lines 13 and 4 there is a pressure-
limiting valve 20. This is so because, when a tree is limbed from
the top towards the base, while the cylinder 18 is moving towards
the open-movement direction, excess oil can pass via line 13 to
return line 14 via the pressure-limiting valve 20. Likewise, the
tree-feeder motor 5 is protected by pressure-limiting valve 20.
Operation on the basis of Figure 1. The gripping of a tree takes
place as follows. Pressurized oil is ed along line 2 from the
power take-off mclchine to the tree harvester 1. Along line 2, oil
can pass only via valve 8 and counterbalance vcllve 12 to
direction-control valves 14 and 15 i~long line 13. The pressurized
oil can Elow further via valve 15 along line 17 into the cylinder
18, which is moving towards the right in the igure.
The movement continues untiL the feeder rolls and the
limbing blades press against the surface of the tree to be
handled, i.e. the desired pressure is effective in the cylinder
18, only thereafter can the crosscut sawing or tree feeding be
started.
The Eeeding in of the tree takes place by feeding
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pressurized oil, for example, via line 3 to the -tree harvester 1
and by a-t the same time energizing valve 14, whereupon pressurized
oil passes via line 3, valve 7, counterbalance valve 11 and valve
14 in order to open valves 7 and 8. ~t the same time, valve 9
closes. Now oil can pass to the tree--feeder motor 5 (there can be
several motors), and the motor begins to rotate in the pre-
selected direction, thereby feeding in the tree. Via valve 11 and
line 13 and valve 15, the pressurized oil in line 3 keeps the
cylinder 18 pressurized, and so the tree is held by the feeder
rolls and the limbing blades. If it is desired to perform a
crosscut sawing, current is cut off from valve 14, whereupon
control pressure in line 19 ceases, and at the same time valves 7
and 8 of the tree-feeder motor 5 close. As the pressurized oil
continues to have e~fect in line 3, valve 9 opens and the saw
motor 6 starts. At the end of the sawing, valve 14 is again
energized, whereupon the valves 7 and a of the feeder motor 5
again open and valve 9 closes. ~y feeding pressurized oil from
the power take~-ofE machille into line ~, val.ve l4 being without
current, whereupon valve 9 of the saw 6 is open but counterbalance
valve 10 prevents the motor 6 from rotating, pressurized oil
passes via counterbalance valve 12 along pipe 13 into valve 15.
When not energized, valve 15 closes, and when energized, it opens
the feeder and the limbing blades by means of the cylinder 18.
Thus, via two electrical cables and three pressurized-
oil pipes, it is possible to control and operate all the functions
of the tree-harvester. This, for its part, facilitates and
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simplifies the coupling oE grapple processors to existing for-
warders, and also reduces the costs. In many forwarders the feed-
ing of oil into lines 2 and 3 can be carried out by using, for
example, the on-off direction-control valve of the grapple.
Furthermore, it is possible advantageously to add the electric
switches of the two direction-control valves 14 and 15 to the
manual lever of this direction-control valve. In the operating
system according to the invention, one pressure-limiting valve 20
suffices for protecting the tree-feeder motor 5 and the hydraulic
cylinder 18 of the feeder and the limbing blades. This for its
part reduces the weight and the space requirement.
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