CA2650748A1 - Hydraulic system for a grapple saw - Google Patents

Abstract

A hydraulic system including a system for enabling a saw motor to operate independently from a set of grapple jaws. Handling equipment provided with the hydraulic system, a method of operating a hydraulic system and/or handling equipment, a kit for assembling the hydraulic system and/or handling equipment and a method of assembling the kit are also described.

Description

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 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.

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 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.

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 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 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.

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 leads to the valve switch 28d of valve 28 and to the valve switch 6d of valve 6.

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 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 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 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 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 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 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 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).

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.

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.

Claims

What is claimed is:

1. A hydraulic system including a system for enabling a saw motor to operate independently from a set of grapple jaws.