Note: Descriptions are shown in the official language in which they were submitted.
CA 02650748 2009-01-23
HYDRAULIC SYSTEM FOR A GRAPPLE SAW
Field of the invention:
The present invention relates to a hydraulic system for handling equipment.
More
particularly, and in its preferred intended use, the present invention relates
to a
hydraulic system for deploying a saw.
Background of the invention:
In the forestry and lumber industry, it is known to provide handling
equipment,
such as a grapple or the like which comprises a pair of opposing jaws for
gripping
and transporting a load, such as logs, trunks or timber. Such jaws are
typically
mounted at the end of a boom, which itself is installed on a vehicle. The
grapple is
opened and closed by actuators such as hydraulic cylinders which are driven by
hydraulic pressure supplied by a pump mounted on a vehicle. In use, a grapple
may be used to pick up one or more logs at a time for transport or primary
processing. Such grapples are commonly installed on vehicles such as loaders,
excavators, material handlers, and the like.
It is known to provide a grapple with a saw arm comprising cutting means for
cutting the logs or other objects held between the grapple's jaws. Typically,
the
saw arm includes a chainsaw comprising an elongate guide, a cutting chain
which
encircles the guide, a saw motor for driving the cutting chain around the
guide, and
a saw actuator for deploying the saw from a retracted position to a deployed
position. The saw motor is typically a hydraulic motor, although other types
of
motors may also be used. The saw actuator is typically a linear hydraulic
actuator,
such as a hydraulic cylinder.
Such grapple saws can be installed on either a positioned or dangling grapple.
During normal operation, the saw is kept within a housing until the operator
activates a saw actuator which deploys the saw, thereby bringing it into
contact
CA 02650748 2009-01-23
2
with the log or logs held by the grapple. Once the saw has passed through the
load it is returned to its housing. While the saw actuator and saw motor are
typically separate mechanisms, it is common to link activation of one to the
other
since the deployment of the saw is typically carried out in conjunction with
operation of the saw motor.
It is often desirable to enable the grapple to rotate freely 360 about the
end of the
boom. As such, a rotational joint, commonly referred to as a rotator, can be
used
which enables such a rotation while also providing internal channels through
which
hydraulic fluid is fed to power the grappling equipment. Such a rotator is
described
in United States Patent No. 7,152,519, issued on December 26th, 2006, to
DUBREUIL.
Also known to the Applicant is US patent No. 5,267,594, issued on December 7tn
1993, to WIEMERI et at.
A conventional rotator typically comprises four internal channels. Two of the
rotator's internal channels are generally used for actuating the jaws of the
grapple
and another two are generally dedicated to the supply and return of hydraulic
fluid
to the saw motor.
It is known to provide a fifth hydraulic line, and hence a fifth hydraulic
channel
within the rotator, to power the saw actuator. However, this increases the
cost and
complexity of manufacturing, assembling, operating and maintaining the
rotator. It
would therefore be advantageous to provide a hydraulic system which did not
require a dedicated fifth hydraulic line.
It is also known to split the hydraulic line powering the saw motor and
thereby
divert power to the saw actuator, however, this reduces the power of the saw
motor. It would therefore be advantageous to provide a system which minimizes
any negative effects that the deploying of the saw actuator might have on the
power supplied to the saw motor.
CA 02650748 2009-01-23
3
It is also known to provide a non-hydraulically powered saw actuator such as
an
electric actuator. However, this also increases the cost and complexity of the
rotator since it requires a rotator capable of conveying an electric power
line and
the addition of an electric power subsystem. It would therefore be
advantageous to
provide a system which did not require an additional electric power subsystem.
It would be advantageous to provide a hydraulic system operable and deployable
with a grapple saw automatically upon activation of its saw motor. It would
also be
advantageous to provide a hydraulic system wherein the saw is activated during
both the deployment and retraction of the saw.
When a saw actuator is not powered by its own dedicated line but rather fed
from
pressure supplied to the grapple jaws and/or the saw motor, conventional
hydraulic systems typically require that various actions taken by the grapple
and
saw occur simultaneously. However, it is known that the saw arm may become
jammed or otherwise immobilized during the cutting cycle. Freeing the saw arm
often requires the operator to break this cycle, at least temporarily. It
would
advantageous to provide a hydraulic system which enables the saw motor to
function while the saw arm remains passive. It would further be advantageous
to
provide a hydraulic system which allows the operator to open the grapple's
jaws
while the saw motor remains in operation.
Hence, in light of the aforementioned, there is a need for an improved system,
which by virtue of its design and components, would be able to address some of
the above-discussed prior art concerns.
Summary of the invention:
An aspect of the present invention is to provide a hydraulic system which, by
virtue
of its design and components, satisfies some of the above-mentioned needs and
CA 02650748 2009-01-23
4
is thus an improvement over other related systems and/or methods known in the
prior art.
According to another aspect of the present invention, there is also provided a
handling equipment provided with the above-mentioned hydraulic system.
Preferably, the handling equipment is a grapple saw.
According to yet another aspect of the present invention, there is also
provided a
method of operating the above-mentioned hydraulic system and/or handling
equipment.
According to yet another aspect of the present invention, there is also
provided a
kit with corresponding components for assembling the above-mentioned hydraulic
system and/or handling equipment.
According to yet another aspect of the present invention, there is also
provided a
method for assembling components of the above-mentioned kit.
According to another aspect of the present invention, there is also provided
material having been processed with the above-mentioned handling equipment.
The objects, advantages and other features of the present invention will
become
more apparent upon reading of the following non-restrictive description of
preferred embodiments thereof, given for the purpose of exemplification only,
with
reference to the accompanying drawings.
Brief description of the drawings:
Figure 1 is a perspective view of a grapple.
Figure 2 is a hydraulic circuit diagram for a hydraulic system according to a
preferred embodiment of the present invention.
CA 02650748 2009-01-23
While the invention will be described in conjunction with preferred
embodiments, it
will be understood that it is not intended to limit the scope of the invention
to such
embodiments. On the contrary, it is intended to cover all alternatives,
modifications
5 and equivalents as may be included, as apparent to a person skilled in the
art in
view of what is described and illustrated in the present description, and what
can
be inferred therefrom.
Detailed description of preferred embodiments of the invention:
In the following description, the same numerical references refer to similar
elements. The embodiments, geometrical configurations, materials mentioned
and/or dimensions shown in the figures or described in the present description
are
preferred embodiments only, given for exemplification purposes only.
In the context of the present description, the expression "handling" includes
all
types of devices for handling and processing materials such as logs and the
like,
which are typical to the forestry industry. Although the present invention was
primarily designed for forestry applications, it may be used with other kinds
of
applications, such as agricultural applications for example, or with any other
items
requiring processing, sorting and/or recovering, as apparent to a person
skilled in
the art. For this reason, the expressions "handling", "forestry", "trees",
"logs", etc.,
should not be taken as to limit the scope of the present invention and
includes all
other kinds of applications or items with which the present invention may be
used
and could be useful.
Moreover, in the context of the present description, the expressions "system",
"device", "assembly", "apparatus" and "unit", as well as any other equivalent
expressions and/or compound words thereof, may be used interchangeably.
In addition, although the preferred embodiment of the present invention as
illustrated in the accompanying drawings comprises various components, and
CA 02650748 2009-01-23
6
although the preferred embodiment of the hydraulic system and corresponding
parts of the present invention as shown consists of certain geometrical
configurations as explained and illustrated herein, not all of these
components and
geometries are essential to the invention and thus should not be taken in
their
restrictive sense, i.e. should not be taken as to limit the scope of the
present
invention. It is to be understood, as also apparent to a person skilled in the
art, that
other suitable components and cooperations therebetween, as well as other
suitable geometrical configurations may be used for the hydraulic system
according to the present invention, as will be briefly explained herein and as
can
be easily inferred herefrom, without departing from the scope of the
invention.
With reference to Figure 1, a grapple 100 is provided with a saw arm 102 which
is
operable to sever material held between a pair of jaws 104. The saw arm 102
comprises an elongate guide 106 and a cutting chain 108 which is driven around
the guide 106 as is known in the art. The guide 106 is pivotally mounted to
the
grapple 100 and pivoted thereabout by an actuator 110 (see Figure 2) from a
retracted position within a housing 114 across the grapple 100 to a deployed
position, and back into the housing. A saw motor 112 (also shown in Figure 2)
is
mounted to the grapple 100 and is operable to drive the chain 108.
It will be appreciated that while the present embodiment comprises a linear
hydraulic actuator 110 to drive the deployment of the saw 102, other types of
actuators are well within the scope of the present invention.
The saw actuator 110 is used to deploy the saw 102 from within the housing and
sweep a cutting path alongside the grapple such that it is comes into contact
and
severs any material held by the grapple 100 which extends beyond the grapple's
grasp. Typically, the saw 102 is used to trim the ends off the gripped a log
or logs.
In the illustrated embodiment, the cylinder 110 is powered by a portion of the
hydraulic pressure used to drive the drive the saw motor 112. The pressurized
hydraulic fluid, for example oil, is diverted to the actuator 110. When the
operator
CA 02650748 2009-01-23
7
activates the saw 102, the cutting chain 108 begins to turn travel, the
cylinder 110
deploys the saw 102 and the grapple jaws 104 are operable to close. When the
operator deactivates the saw 102, a hydraulic accumulator supplies a pressure
to
the opposite side of the cylinder and the saw is retracted.
With reference now to FIG. 2, when an operator activates the saw 102,
pressurized fluid is provided to the saw motor 112 at P. The motor 112 begins
to
turn and the fluid passes through a restriction 2 upon exiting the saw motor
112.
This creates a pressure which is transmitted along line 4 to a port 6c. As
will be
appreciated, valve 6 is preferably a 3/2 valve wherein ports 6a and 6b are
normally
connected while port 6c is initially closed.
The pressure is also transmitted along a line 8 across another restriction 10
to the
stem side 12 of the cylinder 110, but the cylinder 110 does not retract
because of
a pressure which is active at its opposing plunger side 14. This opposing
pressure
is created by a retracting accumulator 16. However, the pressure created by
the
restriction 2 is also transmitted along a line 18 to port 20b of another valve
20. This
pressure crosses the valve 20 to port 20c, along a line 22 and to deploying
accumulator 24. The deploying accumulator 24 is initially empty and therefore
fills
as the motor 102 turns.
Once the accumulator 24 is filled, the pressure therein and along line 18
rises and
engages the valve switch 20d. When engaged, the valve switch 20d switches the
operation of the valve 20, thereby altering the connection of its ports. As a
result,
the transition of the valve 20 begins the descent of the saw warm 102 and the
emptying of the deploying accumulator 24 via the drain line. Once emptied, the
accumulator 24 is ready to be refilled.
The time taken to fill the deploying accumulator 24 delays the actuation of
the
cylinder 110 and therefore the deployment of the saw 102. During that delay,
the
motor 112 turns but the saw arm 102 remains within its housing 114.
CA 02650748 2009-01-23
8
This duration of this delay is function of the volume of the accumulator 24,
the
nitrogen pressure therewithin and the characteristics of the valve 20. It is
therefore
easy to adjust this delay in accordance with, for example, the characteristics
of the
specific grapple 100 to which it is mounted. This delay in deploying the saw
102 is
advantageous if saw 102 becomes jammed or otherwise immobilized during
cutting or during its return. In particular, this problem is known to occur
when the
operator is handling several smaller logs or branches at once.
If the operator becomes aware that the guide 106 has become stuck midway
through its travel because, for example, the wood has shifted within the
grapple
100 during the cut, the operator can deactivate and then reactivate the saw
motor
102. This restarting of the saw motor 112 quickly puts the chain 108 back in
motion but stops the displacement of the guide 106 by the cylinder while the
deploying accumulator 24 refills. The guide 106 is not actively immobilized
however it is merely not pushed/pulled by the cylinder 110. While the
accumulator
24 is refilling, i.e. during the above-mentioned delay, the chain is free to
"bite" into
whatever obstacle is preventing the travel of the guide 106 and, because of
its
geometry, pull itself through that obstacle. This passive approach is
preferred
when forcing the saw 102 into the obstacle may only further tighten the jam.
If at the end of this delay the saw chain 108 has not fully traversed the
obstacle,
the operator is able to perform as many subsequent restarts as necessary.
It will be appreciated that this provides a substantial advantage for the
operator,
who is capable of freeing the guide 106 without having to release the logs
from
grapple 100. Continuing a previous cut after the logs have been dropped is
often
impossible as the logs have become misaligned. Much time is therefore wasted
finishing the interrupted cut.
Once the valve 20 has been switched, the pressure formed by the restriction 2
is
now transmitted from line 18 at port 20b to port 20a and through line 26. Line
26
leads to the valve switch 28d of valve 28 and to the valve switch 6d of valve
6.
CA 02650748 2009-01-23
9
When engaged, these valve switches 28d and 6d alter the state of their
respective
valves 28 and 6. Port 28b is linked to the plunger side 14 of the cylinder 110
via a
line 30. Now switched, the valve 28 opens the port 28b to the port 28c,
thereby
draining the plunger side 14 of the cylinder 110 and allowing the pressure of
the
pressure at the stem side 12 to extend the cylinder 110 and thereby deploy the
saw 102. The restriction 10 serves to limit the pressure supplied to the stem
side
12 and thereby the rate of deployment of the saw arm 102.
For its part, the now switched valve 6 links the port 6c with the port 6b and
allows
the pressure created by the restriction 2 to travel along a line 32 and around
a
restriction 34 to the retracting accumulator 16. The pressure built up in the
retracting accumulator 16 will serve to retract the guide to the housing 114
once it
has completed its cutting.
Once the saw motor 112 is deactivated, the pressure created by the restriction
2
disappears. This drops the pressure in the line 18, which provokes the valve
20 to
switch back to its original position. This in turn drops the pressure in line
26, which
similarly provokes the valves 6 and 28 to switch back to their original
positions.
The hydraulic energy built up and stored in the deploying accumulator 16 is
then
transmitted down line 32, through the restriction 34 which thereby limits the
rate of
retraction of the saw arm 102, and through the valve 28, along line 30 and
back to
the plunger side 14 of the cylinder 110, thereby retracting the guide 106.
Cavitation of the saw motor 112 is prevented by the fluid exiting the stem
side 12
of the cylinder 110 as the saw arm 102 retracts. The fluid passes through an
anti-
cavitation valve 36 and is supplied to the saw motor 112 at P.
In order to commence sawing, the material is first gripped between the jaws of
the
grapple 100. I twill be appreciated however that a load need not be present
between the jaws for the saw 102 to be operated, as is useful when verifying
the
proper functioning of the system for service or maintenance purposes. A set of
proportional levers 38 is provided to control the grapple 100 and manipulate
the
load. The fluid used to control the grapple 100 passes through the valves 40
and
CA 02650748 2009-01-23
42, which are mounted on the loader (or other vehicle). The magnitude of the
pressure is managed by the operator. When the operator closes the jaws 104,
the
control pressure is modulated by the levers 38, and passes through the control
valve 42. The control pressure then travels along a line 44 to the valve
switch 46d
5 of a distributor valve 46 in the auxiliary section of the vehicle.
Pressurised fluid is
thereby free to flow along a line 48, through the rotator 50, to a pair of
grapple
cylinder 52 which actuate each of the jaws 104. As the grapple cylinders 52
extend, the jaws 104 of the grapple 100 close around the load until they have
gripped the log or logs.
As the grapple 100 closes, pressurised fluid passes through a feed-check valve
54, thereby closing a pair of fluid-check valves 56 and 58. The fluid then
travels
through a pressure reducer within a block 60. This allows the grapple
cylinders 52
to operate at a higher pressure than the saw motor 112 if and when the saw 102
is
activated. Until then, however, the fluid will remain in the block 60 because
of a
normally-closed valve 62 which remains closed.
The operator activates the saw 102 by engaging the control valve 42, the valve
62
and a normally-open valve 64. The fluid now flowing through the block 60
passes
along the line 66 and through the port 68 in order to power the saw motor 112.
The
fluid returns from the saw motor 112 along a line 70 and through a check valve
72
to the auxiliary section of the vehicle, while the check valve 58 remains
closed.
The sawing cycle is thereby begun.
If the saw 102 becomes stuck midway through its deployment, the operator can
agitate the load in order to free the guide. This can be done by opening and
closing the jaws without stopping the saw motor 112. In order to do this, the
operator activates the valves 40, 62 and 64. The motor 112 will preferably not
stop
because the transition time of the auxiliary section is very short. The fluid
can flow
back along a line 74 and across the valve 56 instead of the valve 54 which is
now
closed. Nothing will have changed for the fluid passing through the port 68
and it
will continue to drive the saw motor 112. The fluid returning from the saw
motor
CA 02650748 2009-01-23
11
112 will do so along a line 76 via the valve 58 and through the auxiliary
section 46
as the valve 72 will be closed.
It is to be noted, however, that the opening of the jaws 104 while the saw 102
is in
operation cannot last long, as the logs will eventually fall out of the
grapple 100 if it
is opened wide enough. The operator should therefore return quickly, if not
immediately, to the normal sawing mode. It will be appreciated that this
operation
is advantageous in that it enables the operator to free an immobilised guide
and
finish sawing the load. The operator may therefore avoid dropping the load,
picking it back up and starting the sawing operation all over again.
It will be appreciated that a hydraulic system such as the one disclosed
herein is
particularly advantageous for multi-log cuts. The operator is able to free the
saw
arm should it become stuck without wasting the time previously required to
drop
and pick up the load. Because of the delay between the activation of the saw
arm
and its deployment towards the gripped load, the cutting chain is operable to
temporarily advance around the saw guide without being pushed by the saw
actuator. During this interval, the chain may cut enough wood to dislodge the
saw
arm and resume the sawing operation. Another advantage is that the saw is
operable to saw upwards when the chain or guide encounter an obstacle which
prevents it from returning to its housing. As before, this ability avoids
wasting any
time which would previously have been required to drop and pick up the load.
It will be appreciated that the retraction of the saw arm by the embodiment
described hereinabove is automatic. Preferably, the hydraulic actuation of the
cylinder begins immediately after the operator stops the saw motor. The power
diverted to deploy the guide is kept to a minimum. The pressure applied by the
saw cylinder that forces the guide towards the load when the saw motor is
running
also pressurises the retracting accumulator at the same time. During this
period,
the plunger side of the valve is switched and the saw cylinder is connected
with
the drain line and the reservoir. As such, there is no resistance to the
deployment
of the saw arm. The force applied to the saw arm is stable and sufficient to
force
CA 02650748 2009-01-23
12
the guide into a log. After the cut, the energy stored in the retracting
accumulator
drives the saw back into its housing. The retracting accumulator is filled
during the
cutting by the same pressure used to fill the deploying accumulator, i.e. the
pressure created by the restriction 2 on the motor return line 70. By
operating in
this manner, the energy lost is kept to a minimum.
It will be appreciated that the delay mechanism provided by the hydraulic
system
of the embodiment described hereinabove prevents the guide from being
immediately deployed upon starting of the saw motor. Hydraulic oil pressure is
built up along the saw motor's return line thanks to a restriction positioned
along
that line. This pressure is built by passing the motor's outputted fluid
through a
flow control valve which forces fluid to fill a hydraulic accumulator. The
time
required to fill the hydraulic accumulator delays the deployment of the saw.
This
delay is function of the nitrogen pressure of the deploying accumulator and
calibration of the delay valve 20. As such, the length of the delay is easily
adjustable in accordance with each particular application. The hydraulic delay
is
beneficial if the saw guide becomes blocked or remains stuck during the sawing
operation, or during its retraction.
It will therefore also be appreciated that because of the delay mechanism, an
operator has only to stop and restart the saw motor in order to correct the
situation. Because of the delay in deploying the saw arm, the saw actuator
does
not immediately being pushing the saw arm. The cutting means, meanwhile, is
rotating about the guide and is operable to cut the obstacle. Because the saw
is in
contact with the obstacle but remains passive during the delay, the cutting
means
is operable to drive itself into the obstacle because of the geometric
configuration
of its teeth. The cutting means is operable to cut the obstacle which is
preventing
the saw from being retracted. If the saw has not cut the obstacle by the end
of the
delay, the operator may repeat this procedure by restarting the saw motor once
again in order to continue cutting in a passive state. It will be appreciated
that this
provides a substantial advantage to the operator who is thereby able to free
the
saw without having to open the jaws and release the load. As noted, resuming a
CA 02650748 2009-01-23
13
previous cut once a load has been dropped is very difficult. This is
particularly true
when that load comprises a plurality of logs. In this case, it is often
impossible to
resume the previous cut since the fallen logs will fall randomly to the ground
and
much time will be required to finish the original cut.
It will be appreciated that the embodiment described hereinabove enables the
automatic retraction of the saw arm into its original position within the
housing as
soon as the saw motor has been stopped. This retraction mechanism comprises a
group of valves and a hydraulic accumulator. As soon as the deploying
accumulator is filled, the pressure built by the restriction in the motor
return line
provides the power to deploy the saw arm. The saw actuator pivots the saw arm
and advances the saw towards to load held between the jaws. Simultaneously,
the
retracting accumulator is filled by the same return line pressure. As soon as
the
saw motor is deactivated, the retracting accumulator releases the hydraulic
fluid
and pressure built up therewithin in order to raise the saw arm. This cutting
cycle
is entirely automatic and repeatable. This retraction mechanism includes a
group
of valves, as well as a device which allows the saw arm to be manually
released
from its housing in order to, for example, conduct maintenance or replace the
chain. The energy stored within the accumulator, used during operation to keep
the saw within its housing, is discharged. It will be appreciated therefore
that this
provides an easy access to the operator and greatly improves safety.
It will be appreciated that the embodiment described hereinabove further
comprises a grapple mechanism which allows the saw to operate while the
grapple is partially open. A load is held between the grapple's jaws by
hydraulic
pressure during the sawing operation to prevent that material from moving.
However, should the saw become caught or jammed, it may be useful to partially
open the grapple and/or loosen its grip on the load held between its jaws,
while
continuing to advance the saw therethrough. As such, the saw motor must remain
in operation so that the cutting chain continues to turn while the saw arm
finishes
its deployment. This apparatus comprises a group of four anti-return valves
(also
referred to as check valves) and two guide valves (also referred to as pilot
valves).
CA 02650748 2009-01-23
14
There are two anti-return valves installed on the grapple and two within the
saw
command valve installed on the vehicle. Through the operation of the two guide
valves, the operator may partially open the grapple and subsequently close it
without needing to stop the saw motor.
It will be appreciated that the embodiment described hereinabove integrates
the
delay mechanism, the retraction mechanism and the grapple mechanism into a
single operational system. The hydraulic system is entirely adjustable and
adaptable to various applications, in accordance, for example, with the
variety of
wood being harvested, the size of the logs being handled, or the other
variations in
the size and shape of the grapple and grapple saw. The rate at which the saw
arm
is deployed and retracted may also be optimised by the components of the
system. These same components prevent the saw motor from stopping abruptly
when the chain comes into contact with the grapple's load.
It will further be appreciated that the hydraulic system described herein
allows for
a more efficient management of the power provided to the saw arm. The power
required to deploy and retract, which typically involves a lowering and a
raising, is
limited as much as possible. No more pressure is used than is necessary in
order
to ensure that the saw arm is properly deployed. As a result, the pressure
saved
by the saw actuator is supplied to the saw motor in order to further power the
cutting. There is therefore less burden placed on the vehicle's engine,
typically a
diesel engine which runs the hydraulic system's pump, and as such the
operating
cost of the system is reduced. Moreover, the major components of the saw and
the hydraulic motor all work in an appropriate environment. In fact, the this
system
reduces the pressure on the return side which in turn will extend the life of
the
motor.
The illustrated embodiment relates to a grapple for handling logs and felled
trees,
although it will be appreciated that the hydraulic system described herein is
applicable in other embodiments such as on feller heads and the like.
CA 02650748 2009-01-23
Of course, numerous modifications could be made to the above-described
embodiments without departing from the scope of the invention, as apparent to
a
person skilled in the art.
