Method of loading timber logs on a log-handling vehicle and a log-handling vehicle

Abstract

The invention relates to a log-handling vehicle and a method for loading logs on a log- handling vehicle in which is implemented a controller (24), controlling a closing pressure (P) of a grapple actuator (4c), when detecting that the closing pressure (P) has reached an upper pressure threshold (P-thres 2), automatically controlling the grapple actuator (4c) to assume stopped movement by controlling the grapple valve (18) to shut to inhibit flow to the grapple actuator (4c), when detecting that the provided pressure indication has fallen below a lower pressure threshold (P-thres 1), automatically controlling the grapple actuator to assume closing movement by controlling a grapple valve to re-open to allow a hydraulic flow to the grapple actuator (4c) to close the grapple (4) around the log, lifting the grapple (4) by an articulated crane (2), when the grapple actuator (4c) has assumed stopped movement, providing from the pump system a hydraulic flow at a hydraulic pressure less than the upper pressure threshold (P-thres 2), via a valve system (13, 13A, 13B), to at least one of a grapple rotator (2b) and the crane rotator (2a).

Description

[0001] METHOD OF LOADING TIMBER LOGS ON A LOG-HANDLING VEHICLE AND A LOGHANDLING VEHICLE

[0002] AREA OF TECHNOLOGY

[0003] The present invention relates to a method of loading logs on a log-handing vehicle according to claim 1. The invention also relates to a log-handling vehicle according to claim 7.

[0004] BACKGROUND OF THE INVENTION

[0005] Regarding forest machines in general, there is a constant development towards increased productivity, energy efficiency and minimization of exhaust emissions. Not least, an ongoing conversion from today's internal combustion engines to hybrid electric, or battery-powered forestry machines place increased demands on efficient energy utilization and avoidance unnecessary energy losses.

[0006] A forestry machine such as a forwarder, timber truck or similar vehicle for log-handling and transport has a log-carrying compartment and a crane with a clawed grapple for handling timber to and from the log-carrying compartment. In cut-to-length logging, a forwarder manipulates log loads with its crane and grapple a significant portion of its total operating time. Usually, an operator of such a forwarder has two control levers (joysticks) to control and direct the movements of the crane and grapple. Typically, one of the control levers has, on one of its side surfaces, a control device in the form of a thumb button switch (also referred to herein as a rocker switch, a three-way switch, and in a general sense an operator-input device) with spring return to center position. This control device allows the operator to generate different commands by switching between the following three operating modes: opening-of-grapple or closing-of-grapple (the thumb button switch is rocked / rotated in one direction or the other), and no grapple movement (the thumb button switch is unaffected and rests in its center position). The control device is normally of a proportional type, wherein an amount of rotation of the thumb button switch is recorded and a speed of movement of the grapple jaws is generally controlled to be proportional thereto and is accessible for actuation with the thumb without the operator needing to release the grip on the control lever. Typically, this speed corresponds to a hydraulic flow rate to the grapple actuator, although the inter-dependency might be nonlinear.

[0007] In today’s forwarders, typically, the manipulation of log loads is controlled manually by the operator (driver). To close grapple, the operator presses the thumb switch of the control device, which in response generates an operational command signal Z+. In response to the operational command signal Z+, a control signal is generated to a hydraulic valve whereby ahydraulic flow is applied to an actuator which closes the grapple. A hydraulic flow will be directed to the actuator and a high pressure will build up in the actuator as the grapple closes around a load of logs. If the grapple is kept closed by maintaining the command signal Z+ (for instance at 100%), the forwarder’s hydraulic pump system will work continuously at a high-pressure. This is likely to cause unnecessary consumption of hydraulic power. Due to the location and function of the control device on the side surface of the control lever, the operator still tends to maintain the closing command position Z+, even after the grapple has closed to a stationary position around a log load and while the operator with the control lever directs and controls the movements of the crane during timber handling. Typically, in the context of this disclosure, the crane is non-static while the grapple is kept closed around a log load. On the contrary, different parts of the crane move constantly or almost constantly during the grapple’s holding of a log load, when loading (or unloading) the log-carrying compartment. Maintaining the closing-of-grapple operating mode means that a hydraulic valve feeding the grapple actuator is also open and that the forwarder’s pump system is set to deliver a high pressure to the log grapple actuator when closed. This means that any other hydraulic consumer sharing its hydraulic pressure source with the grapple actuator, but requiring a lower pressure, must be provided with its hydraulic flow via pressure-reducing throttling. Such throttling causes energy losses that are desirable to reduce during the of loading logs onto a log-handing vehicle’s load-carrying compartment through improved crane and grapple control.

[0008] SUMMARY OF THE INVENTION

[0009] At least problems outlined or implicated above are alleviated by a method of loading logs on a log-handing vehicle, wherein the vehicle comprises: a frame, a propulsion system, and a logcarrying compartment on top of the frame, said log-carrying compartment being arranged to carry logs in a main direction; a controller arranged to control a hydraulic system of the vehicle, said hydraulic system comprising: an articulated crane rotatably mounted at its base to the frame via a hydraulic crane rotator, said crane having a grapple attached at the tip of the crane via a hydraulic grapple rotator, a hydraulic grapple actuator arranged to perform opening movement, closing movement, or stopped movement of the grapple, a pressure sensor arranged to provide a pressure indication of a hydraulic closing pressure of the grapple actuator, a hydraulic pump system and a hydraulic valve system, said hydraulic valve system having a grapple valve arranged to control a hydraulic flow from the hydraulic pump system to the grapple actuator to control the grapple’s movements; wherein the method is implemented in the controller and the method comprises the steps of: controlling the grapple actuator to perform closing movement around a log (generally to be understood as one or several logs) by controlling the hydraulic flow through the grapple valve to the grapple actuator andmonitoring said pressure indication; when detecting that the closing pressure has reached an upper pressure threshold value, automatically controlling the grapple actuator to assume stopped movement by controlling the grapple valve to shut to inhibit flow to the grapple actuator; when detecting that the provided pressure indication has fallen below a lower pressure threshold value, automatically controlling the grapple actuator to assume closing movement by controlling the grapple valve to re-open to allow a hydraulic flow to the grapple actuator to close the grapple around the log; lifting the grapple by the articulated crane; when the grapple actuator has assumed stopped movement, providing from the pump system a hydraulic flow at a hydraulic pressure less than the upper pressure threshold value, via the valve system, to at least one of the grapple rotator and the crane rotator; aligning the log with the main direction by the grapple rotator and the crane rotator; lowering the grapple by the articulated crane; controlling the grapple actuator to perform opening movement to release the log in the log-carrying compartment by controlling the hydraulic flow through the grapple valve to the grapple actuator. Similarly, the problems are alleviated by the inventive log-handling vehicle, in which the controller is arranged to perform the method.

[0010] Advantageously, the invention may further (or as an alternative) comprise the following combination when the grapple actuator has assumed stopped movement: providing from the pump system a hydraulic flow at a hydraulic pressure less than the upper pressure threshold value (optionally, below the lower pressure threshold value), via the valve system, to at least one of the grapple rotator and the crane rotator; and providing from the pump system a hydraulic flow at a hydraulic pressure less than the upper pressure threshold value (optionally, below the lower pressure threshold value) and at least temporarily different to that provided to at least one of the rotators, via the valve system, to at least one further actuator of the crane other than a rotator. Optionally, when the grapple actuator has assumed stopped movement, the provision of such hydraulic flows at different pressures from the pump system is realized by different pumps of the pump system providing different hydraulic pressures. This enables avoidance of throttling and associated losses. The above further features may be combined in any manner with other claimed or unclaimed features disclosed herein.

[0011] The method steps disclosed herein may be consecutive, non-overlapping, overlapping, and / or simultaneous, unless logically unfeasible. This also applies to combinations with further method steps, also including steps not explicitly mentioned herein, conventionally performed in a log-handling vehicle of the type disclosed herein.

[0012] For the automatic control to work well, the upper pressure threshold value should be at least somewhat lower than a maximum (actual or predetermined) pressure that the pump system may delivering to the grapple actuator. The hydraulic closing pressure may temporarily over-shoot the upper pressure threshold value.The inventive automation or semi-automation of certain aspects of crane manipulation ensures a more efficient energy utilization, beneficial not least in hybrid electric or battery-powered log-handling vehicles. Further, the automatic control when holding a log in the grapple alleviates demands on the operator’s active control and monitoring of the crane and grapple.

[0013] According to an embodiment the hydraulic flow provided to said at least one of the grapple rotator and the crane rotator, when the grapple actuator has assumed stopped movement, is provided with a hydraulic pressure less than the lower pressure threshold value.

[0014] According to an embodiment, the lower pressure threshold value is less than 95% of the upper pressure threshold value. A range of less than 80% through less than 99% could be suitable.

[0015] According to another embodiment the method comprises, receiving in the controller a command, on which to base the control movements of the grapple, said command being at least one of: a closing grapple command (CLOSE GRAPPLE = ON), an opening grapple command (OPEN GRAPPLE = ON), a stopping grapple command (CLOSE GRAPPLE = OFF), and, optionally, a closing grapple speed command, an opening grapple speed command.

[0016] According to an embodiment, the commands comprise, operator-input commands and / or system commands generated by a computer-implemented task manager.

[0017] According to another embodiment, the method comprises, when the closing grapple command is being received in the controller, repeating the steps of: when detecting that the provided closing pressure has reached the upper pressure threshold value, automatically controlling the grapple actuator to assume stopped movement by controlling the grapple valve to shut to inhibit flow to the grapple actuator; when detecting that the provided pressure indication has fallen below the lower pressure threshold value, automatically controlling the grapple actuator to assume closing movement by controlling the grapple valve to re-open to allow a hydraulic flow to the grapple actuator to close the grapple around the log. Leakage of hydraulic fluid inside the grapple actuator and spontaneous rearrangement of a log load are examples of causes of a falling pressure indication.

[0018] According to another embodiment, the hydraulic flow provided to said at least one of the grapple rotator and the crane rotator, when the grapple actuator has assumed stopped movement, is provided with a hydraulic pressure less than the lower pressure threshold value. Typically occurring such hydraulic pressures of the rotators could include a range of 10% through 90% of the lower pressure threshold value. The occurrence of such hydraulic pressures outside and even well above this range are not ruled out.

[0019] According to an embodiment, further comprising an operator-input device arranged to provide operator-input commands to the controller to render closing or stopped grapple movement, as long as actively maintained by the operator, wherein, optionally, the operator-input device further comprises a control lever for controlling at least one of the grapple rotator and the crane rotator.

[0020] According to another embodiment, on a side surface of the control lever is provided a control device which, through operator-input commands, allows switching between: a closing grapple command (CLOSE GRAPPLE = ON) , an opening grapple command (OPEN GRAPPLE = ON), a stopping grapple command (CLOSE GRAPPLE = OFF), and, optionally, a closing grapple speed command and an opening grapple speed command.

[0021] According to an embodiment, the side surface of the operator-input device comprises a thumb button / three-way switch with spring-loaded return to center position for affecting the operator-input commands.

[0022] According to another embodiment, the hydraulic pump system comprises at least one of the following combinations: a flow-controllable hydraulic pump driven by an internal combustion engine (ICE), a fixed displacement hydraulic pump driven by a speed controllable electric motor.

[0023] According to an embodiment, the log-handling vehicle is a one of: a cut-to-length-logging harvester vehicle and a log-forwarder vehicle, and wherein the hydraulic pump system comprises a hydraulic pump common to the grapple actuator and at least one of, the grapple rotator, the crane rotator, a main boom actuator between a crane base and a main boom of the articulated crane, a knuckle boom actuator between a main boom and a knuckle boom of the articulated crane, and a telescopic boom actuator of the knuckle boom of the articulated crane.

[0024] According to another embodiment the hydraulic system comprises first and second separable hydraulic valve groups, respectively, coupled via first and second hydraulic circuits, respectively, to the hydraulic pump system, wherein of the first valve group provides hydraulic flow to the crane rotator, the grapple rotator, and the telescopic boom actuator of the knuckle boom of the articulated crane and wherein the second valve group provides hydraulic flow to the grapple actuator, the main boom actuator between a crane base and a main boom of the articulated crane, and the knuckle boom actuator between a main boom and a knuckle boom of the articulated crane.

[0025] According to an embodiment, the log-handling vehicle is configured allow the automatic controlling of the grapple actuator occur predominantly during a log-loading sequence comprising a first closing of the grapple around the log, manipulations of the log by the articulated crane, and a first releasing of the log aligned in the main direction in the logcarrying compartment.

[0026] Optionally, grapple yawning may be monitored.In case monitoring of the grapple, when the flow to its actuator is inhibited and the grapple is carrying a load, the decision may be based solely on the yawning position indication. This has the consequence that the pressure sensor may not need to be able to sense the pressure inside the grapple actuator. In this situation, a change in the yawning position indication is treated as an indication of a change (a lowering) in the pressure in the grapple actuator. In this situation, if there is a leakage in the grapple actuator (and typically a resulting fall in pressure), a slight increase in the grapple yawning position can be expected to occur. In this situation, if there is a spontaneous re-arrangement of the load inside the grapple actuator (and typically a resulting fall in pressure), a slight decrease in the grapple yawning position can be expected to occur. This increase or decrease in the yawning position (detectable by corresponding change in the yawning position indication) is thus usable for controlling re-pressurizing the grapple actuator after re-opening of the grapple valve. Based on the above, the skilled person appreciates how monitoring of pressure indication of the closing pressure in the grapple actuator could optionally be combined with monitoring of the yawning position indication in order to improve the operation of the grapple to save energy when performing the workflows of loading and un-loading logs.

[0027] Further, a reliance solely on either the pressure indication (inside the grapple actuator) or the yawning position indication is included in the inventive scope.

[0028] It should be noted that the hydraulic system, which provides hydraulic flow to the grapple actuator, typically includes one or several pressure sensors capable of monitoring pressure in the grapple actuator as long as the grapple valve is open. That pressure sensor could constitute the pressure sensor for providing the pressure indication of the hydraulic closing pressure of the grapple actuator, in case there it is not prioritized to sense the pressure inside of the grapple actuator.

[0029] Grapple yawning monitoring is used herein to monitor the amount of opening of the grapple, more particularly a separation of the claws of the grapple. A yawning position sensor (which could include several sensor units) could be located on the grapple actuator to sense the linear position thereof (or on each grapple actuator if the grapple claws require several actuators) or be located in connection to a rotational axis of each grapple claw.

[0030] Such sensor or sensors located on the grapple may require radio communication means or a wired connection fed through the grapple rotator to communicate with the controller.BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In the following, the invention is described in more detail with the guidance of an embodiment shown in the attached drawings; on which.

[0032] Fig. 1 shows a perspective view of a log-handling vehicle in the form of a so-called forwarder which carries a grapple for handling timber at the free end of a crane and is configured with an adaptive automatic load holding function which is controlled in accordance with the present invention.

[0033] Fig. 2 shows a perspective view of an end part of the crane in which the grapple is suspended, in which a closer view is shown of a timber grapple actuator which is operatively connected to the grapple's mutually movable grapple claws for maneuvering them between an open and a closed position.

[0034] Fig. 3A schematically shows a block diagram of an electrohydraulic control system for adaptive control of the grapple's automatic load holding function in accordance with the present invention.

[0035] Fig. 3B schematically shows how the hydraulic system can comprise a first and a second separate hydraulic valve group, connected via first and second hydraulic circuits respectively to a common hydraulic pump system but configured to supply different consumers in the log-handling vehicle with hydraulic flow.

[0036] Fig. 4 schematically shows a flowchart of program control for cyclic commanding of the grapple in automatic load holding mode with control of the current fluid pressure in the grapple hydraulic actuator according to the invention.

[0037] Fig. 5A, 5B shows schematically during a second operating condition with automatically controlled load holding how a controller regarding a determined maximum pressure automatically switches between operating mode, closing grapple and no grapple movement.

[0038] Fig. 6 graphically shows the operating mode when switching between a firstoperating mode with operator command-controlled load holding and a second operating mode with automatically controlled load holding with respect to a determined threshold value pressure and further in which way during said second operating mode a controller with respect to a determined maximum pressure automatically switches between operating mode, closing grapple or no grapple movement.

[0039] DETAILED EMBODIMENT DESCRIPTION

[0040] Fig. 1 shows a timber or log-handling vehicle 1, which here constitutes a forwarder, but which could of course include any vehicle equipped with a crane 2 and log-carryingcompartment 3 which, at a free end of said crane, carries a grapple unit rotatable around a vertical axis, hereinafter referred to grapple 4 for handling timber. In an alternative embodiment, the timber handling vehicle could comprise a timber truck or the like.

[0041] The timber handling vehicle 1 having a frame comprising a front 1A and a rear 1B vehicle unit, respectively, which are hingedly connected via a control joint 1C. On its respective chassis, the front vehicle unit 1A supports a superstructure which essentially comprises an engine 5 forming part of a propulsion system generally designated with 7 and a driver's cab 6, while the rear vehicle unit 1B supports a superstructure which mainly comprises said crane 2 with associated hydraulic cylinders and said loading space or log-carrying compartment 3 for timber 9. On the free end of the crane 2 is grapple 4 pivotably suspended via a joint connection 10.

[0042] As can best be seen from Fig. 2, grapple 4 comprises pair-acting grapple claws 4a, 4b and a double-acting timber grapple cylinder or a hydraulic grapple actuator 4c (see detailed enlargement in Fig. 2), which timber grapple cylinder is operatively connected to the grapple 4 for the grapple claws 4a, 4b to be pivotable to a receiving or log collection mode and pivotable to a log grapple position.

[0043] In Fig. 3A, a hydraulic system of the vehicle is generally designated by 20. The hydraulic system comprise a hydraulic crane rotator 2a and a hydraulic grapple rotator 2b attached at the tip of the crane before the grapple 4. The hydraulic system which controls the operation of the grapple 4 is shown in more detail, and more specifically a control system that automatically controls the operation of the grapple 4 by means of hydraulic fluid pressure feedback and the operator's control commands when opening / closing the grapple or no grapple movement. The hydraulic components of control system 20 essentially comprise a pressure medium source in the form of a pump 15 which is driven by engine 5 and sucks hydraulic fluid from tank 16. In an alternative embodiment encircled with a dashed line the hydraulic pump can be a fixed displacement hydraulic pump 15’ driven by a speed controllable electric motor 5’.

[0044] Reference numerals 13A, 13B in fig. 3B denotes hydraulic valve system for controlling hydraulic fluid from a pump system 12 to at least one of the grapple rotator 2b and the crane rotator 2a. It should be understood that the hydraulic pump system 12 comprises a hydraulic pump 15 common to the grapple actuator 4c and at least one of, the grapple rotator 2b, the crane rotator 2a, a main boom actuator 2c between a crane base and a main boom of the articulated crane 2, a knuckle boom actuator 2d between a main boom and a knuckle boom of the articulated crane, and a telescopic boom actuator of the knuckle boom of the articulated crane. Also, it should be understood that the hydraulic system comprises first and second separable hydraulic valve groups, respectively, coupled via first and second hydraulic circuits, respectively, to the hydraulic pump system, wherein of the first valve group provides hydraulicflow to the crane rotator 2a, the grapple rotator 2b, and the telescopic boom actuator of the knuckle boom of the articulated crane and wherein the second valve group provides hydraulic flow to the grapple actuator 4c, the main boom actuator between a crane base and a main boom of the articulated crane 2, and the knuckle boom actuator 2d between a main boom and a knuckle boom of the articulated crane.

[0045] Again, with reference to fig. 3A, via an electromagnetic grapple valve 18 of the fourway three-position valve type with proportional distribution of flow, the hydraulic fluid is distributed to the grapple 4 timber grapple cylinder 4c for maneuvering of the grapple claws 4a, 4b. The grapple's 4 claws 4a, 4b are closed to grasp the timber 3 and allow the timber to be lifted with the crane 2. The swinging movements of the grapple claws 4a, 4b between an open and closed position for the grapple 4 are controlled by the log grapple cylinder 4c via grapple valve 18.

[0046] The grapple valve 18 controllably operates the grapples 4 actuator 4c. A control lever 23a is used for controlling movements of the crane 2. On a side surface of the control lever 23a, there is a control device 23b in the form of a thumb button / three-way switch with a spring-loaded return to the center position and which, through operator commands, allows switching between the following three working modes, opening / closing Z+, Z- of grapple 4 when the thumb button / three-way switch is activated, respectively none grapple movement 0 in center position when thumb button / three-way switch 23b is deactivated.

[0047] The timber grapple cylinder 4c is controlled in response to an operational command signal Z from said control device 23b and a microprocessor-based control unit or controller 24 which is connected to the grapple valve 18. The control unit 24 is equipped with a calculation unit and a memory unit for storing program code and data (not shown). The control device 23b is controlled with the operator's thumb and is used primarily for manual control of the grapple movements between the working mode open grapple Z- and working mode close grapple Z+, in the following command "OPEN GRAPPLE" or the "CLOSE GRAPPLE" command.

[0048] In the detailed enlargement at the top and to the right of Fig. 3A, the control device 23b is shown more closely and how the operative command signal Z+ "CLOSE GRAPPLE" during manual load holding is generated.

[0049] Switching from a first operating state A and operator-controlled manual load holding in the grapple to a second operating state B and automatic command-controlled load holding in the grapple takes place by detecting a full command signal on the control device 23b for the command signal Z+ "CLOSE GRAPPLE". Sensing takes place by receiving a pressure indication indicating a current fluid pressure P in the grapple cylinder 4c that operates the grapple 4, based on the fluid pressure it is determined whether the grapple 4 is in working position closing Z+ with a full signal on the control device 23b, and in that case the control unit 24 is switched to work in a second operating state B with automatic command-controlledswitching between the working mode closing Z+ of grapple and no grapple movement 0 of grapple. By sensing the current fluid pressure P and / or pressure increase rate dP and comparison with a threshold value P-thres, it is determined whether the operative command signal Z+ "CLOSE GRAPPLE" is a full signal or not.

[0050] As illustrated in Fig. 6, the duration of the operative command signal Z+ can be derived by means of the control unit 24 and the pressure sensor 22 detecting and analyzing data from occurring pressure P and / or pressure changes in the timber grapple cylinder 4c, commanding from the first operating condition A with manual load holding to the second operating condition B with automatic load holding takes place automatically in the control unit 24.

[0051] In accordance with the invention, a current pressure P or a pressure development in the timber grapple cylinder 4c of the claws 4a, 4b is used not only for switching between operating state A (manual load holding) and operating state B (automatic load holding), but also for generating the control signal CS to the grapple valve 18 for automatic operation of the grapple claws 4a, 4b when the system is switched to operating mode B and automatic load holding.

[0052] Fig. 3B shows in more detail an example of how switching from the first operating state A (manual load holding) and the second operating state B (automatic load holding) takes place by means of current pressure P in the grapple claws 4a, 4b timber grapple cylinder 4c. Control unit 24 is configured to determine, during the second operating condition B, whether the current pressure P in the grapple cylinder 4c is below the threshold value P-thres 1 , and if so return to working in the normal first operating condition A. Furthermore, it appears how the control unit 24 is configured to when working in the second operating state B, guided by fluid pressure feedback from the grapple cylinder 4c, generate a load holding control signal CS to the grapple valve18 to automatically operate the grapple 4 in the working position, closing grapple Z+ if the current fluid pressure P falls below a predetermined lower pressure level P-thres 1, i.e. P<P-thres 1 or the working mode, no grapple movement 0 if the fluid pressure exceeds the predetermined upper pressure level P-thres 2, i.e. P>P-thres 2.

[0053] Fig. 5A, 5B shows schematically how regulation takes place by the grapple's pairacting claws 4a, 4b switching between the functional modes "CLOSE-GRAPPLE = ON" and "CLOSE-GRAPPLE=OFF" respectively in automatic load holding mode guided by the actual fluid pressure P in the grapple claws 4a, 4b log grapple cylinder 4c.

[0054] Reference is now made to Fig. 4, which illustrates a flow diagram of how a pressure indication indicating a current fluid pressure in the grapple cylinder enables adaptive switching from operator command-controlled load holding to automatically controlled load holding. Namely by normally working in a first operating state A with operator command-controlled switching between said three working modes Z+, Z-, 0 of the grapple 4, to receive a pressureindication indicating a current fluid pressure P in the grapple cylinder 4c which operates the grapple 4, and by comparing with an upper threshold value P-thres 2 determine if the grapple 4 is in the working mode closing Z+ with full signal on the controller 23b, and if so operate in a second operating state B with automatic command-controlled switching between the working mode closing Z+ of the grapple and no grapple movement 0 of the grapple based on fluid pressure feedback from the timber grapple cylinder 4c and during which second operating condition B the control unit 24 automatically switches between said working modes by comparing the current fluid pressure P in the timber grapple cylinder 4c with said upper threshold value P-thres 2 and a lower threshold value P-thres 1.

[0055] The program depicted in the flowchart is adapted for use as software in any suitable microprocessor system.

[0056] A pressure sensor 22 detects the actual value of the fluid pressure P in the timber grapple cylinder 4c during the first operating condition A and generates a pressure signal which is representative thereof. The control unit 24 receives information about the operational command signal's Z+ magnitude and generates control signals CS to the hydraulic system's pump 15 and grapple valve 18. About the operational command signal's Z+ magnitude value at the closing command, grab Z+ in the first operating state A with manual load holding. If the command is a full command signal on the controller 23b, i.e. the fluid pressure in the log grapple cylinder 4c rises rapidly and exceeds the upper threshold value P-thres 2 automatically switching to the second operating state B with automatic load holding mode is commanded.

[0057] At decision block S1, the program starts by determining the operating condition of grapple 4 when operating in its normal first operating state A with manual load holding and operator controllable control commands such as closing grapple Z+, opening grapple Z- and no grapple movement generated by operational command signals from controller 23.

[0058] In step S2, program control determines the current operational status of the control device 23 at the command of the control function closing grapple Z+ is a full command signal or not, based on the current fluid pressure P in the log grapple cylinder 4c. If the fluid pressure P in the timber grapple cylinder 4c exceeds the upper threshold value P-thres 2, the command signal is perceived as a full command signal, whereby the system switches from the first operating state A but manual load holding to the second operating state B with automatic load holding, after which the program continues to step S3. If this is not the case, the program returns to the decision block in step S1.

[0059] In step S3, a pressure indication of the current fluid pressure P in the timber grapple cylinder 4c is received.

[0060] In step S4, it is compared whether the current fluid pressure P in the log grapple cylinder 4c exceeds a predetermined upper threshold value P-thres 2 in the log grapplecylinder 4c, whereby the pressure value P is higher than determined, the program continues to step S5.

[0061] In step S5, the control function "CLOSE GRAPPLE" = OFF" is initiated, in which the grapple valve 18 is deactivated and a reduction of the pump pressure can also be commanded, while if the pressure P is lower than P-thres 2, the program continues to step S6.

[0062] In step S6, it is compared whether the current fluid pressure P in the log grapple cylinder 4c falls below a predetermined lower pressure value P-thres 1 in the log grapple cylinder 4c, whereby the pressure value P is lower than determined, the program continues to step S7.

[0063] In step S7, the control function "CLOSE GRAPPLE = ON" is initiated, in which the grapple valve 18 is activated and an increase in the pump pressure can also be commanded.

[0064] Said predetermined upper pressure level P-thres 2 can lie in a range of between 260 and 235 MPa, while the lower threshold value P-thres 1 can lie in a range between 200 and 180 MPa.

[0065] The pressure sensor 22 arranged to provide a pressure indication of a hydraulic closing pressure of the grapple actuator 4c may be connected to the grapple actuator and arranged to sense the hydraulic pressure therein.

[0066] Note that the program cyclically restarts as soon as it initiates the automatic shutdown function and that program blocks S1-S7 are executed continuously. Consequently, the pump runs automatically in high pressure mode, without operator intervention and only when high pressure is needed, which saves valuable engine power and offers an improved energy yield and increased efficiency of the machine.

[0067] In Fig. 3A, 30 denotes a computer-readable medium comprising software instructions 31 , which, when loaded into and executed by the control unit 24, causes execution according to the patent claim to carry out the cyclic process steps specified above.

[0068] Optionally, grapple yawning may be monitored. In this case, a yawning position sensor 26, 27 is arranged to provide a yawning position indication of the grapple’s 4 current yawning position. The yawning position sensor 26, 27 may be a sensor 26 arranged at the grapple and / or a sensor 27 arranged at the grapple actuator.

[0069] For example, when being arranged at the grapple, the sensor 26 may be a rotary position sensor. The position sensor arranged at the grapple may be a non-contact sensor, such as a magnetic sensor, inductive sensor, or optic sensor. The sensor arranged at the grapple may be a contact-based rotary position sensor such as a rotary potentiometer.For example, when being arranged at the grapple actuator, the sensor 27 may be a position sensor arranged to sense the extension of the actuator. The sensor 27 may be a non-contact sensor, such as a magnetic sensor, inductive sensor, or optic sensor. The sensor 27 may be contact-based, such as a potentiometer.

[0070] The sensor arrangement may comprise a camera (not shown) arranged to capture images of the grapple and / or grapple actuator and a processor arranged to process the captured images to determine a value relating to how closed the grapple is.

[0071] The sensor(s) 26, 27 may be arranged to communicate with the control unit 24 via cable or wirelessly. The sensor(s) 26, 27 may be arranged communicate sensor data to the control unit. The sensor(s) 26, 27 may comprise a processor performing pre-processing of the sensor data before transmission to the control unit 24.

[0072] The method implemented in the controller 24 may comprises the following:

[0073] The grapple actuator 4c is controlled to perform closing movement around a log by controlling the hydraulic flow through the grapple valve 18 to the grapple actuator and the pressure indication is monitored.

[0074] In case of grapple yawning monitoring, said yawning position indication is monitored.

[0075] In case of grapple yawning monitoring, when detecting that the yawning position has become static, the grapple actuator (4c) may be automatically controlled to assume stopped movement by controlling the grapple valve (18) to shut to inhibit flow to the grapple actuator (4c). Instead or in addition thereto, when detecting that the closing pressure (P) has reached an upper pressure threshold value (P-thres 2), the grapple actuator (4c) may be automatically controlled to assume stopped movement by controlling the grapple valve (18) to shut to inhibit flow to the grapple actuator (4c).

[0076] in case of grapple yawning monitoring, when detecting that the yawning position has changed by at least a predetermined opening amount or at least a predetermined closing amount, the grapple actuator may be automatically controlled to assume closing movement by controlling the grapple valve (18) to re-open to allow a hydraulic flow to the grapple actuator (4c) to close the grapple (4) around the log. Instead or in addition thereto, when detecting that the provided pressure indication has fallen below a lower pressure thresholdvalue (P-thres 1), the grapple actuator may be automatically controlled to assume closing movement by controlling the grapple valve (18) to re-open to allow a hydraulic flow to the grapple actuator (4c) to close the grapple (4) around the log.

[0077] The grapple 4 is then lifted by the articulated crane 2.

[0078] When the grapple actuator 4c has assumed stopped movement, a hydraulic flow is provided from the pump system 12 at a hydraulic pressure less than the upper pressure threshold value (P-thres 2), via the valve system 13, 13A, 13B to at least one of the grapple rotator (2b) and the crane rotator (2a). Thus, even in a situation where detection that the closing pressure (P) has reached an upper pressure threshold value (P-thres 2) is not used, it is assumed that that the hydraulic flow is provided from the pump system 12 at a lower pressure than such upper pressure threshold value.

[0079] The log is then aligned with the main direction by the grapple rotator 2b and the crane rotator 2a.

[0080] The grapple is thereafter lowered by the articulated crane 2.

[0081] The grapple actuator 4c is the controlled to perform opening movement to release the log in the log-carrying compartment 3 by controlling the hydraulic flow through the grapple valve 18 to the grapple actuator 4c.

[0082] In case monitoring of the grapple, when the flow to its actuator is inhibited and the grapple is carrying a load, the decision may be based solely on the yawning position indication. This has the consequence that the pressure sensor may not need to be able to sense the pressure inside the grapple actuator. In this situation, a change in the yawning position indication is treated as an indication of a change (a lowering) in the pressure in the grapple actuator. In this situation, if there is a leakage in the grapple actuator (and typically a resulting fall in pressure), a slight increase in the grapple yawning position can be expected to occur. In this situation, if there is a spontaneous re-arrangement of the load inside the grapple actuator (and typically a resulting fall in pressure), a slight decrease in the grapple yawning position can be expected to occur. This increase or decrease in the yawning position (detectable by corresponding change in the yawning position indication) is thus usable for controlling re-pressurizing the grapple actuator after re-opening of the grapple valve. Based on the above, the skilled person appreciates how monitoring of pressure indication of the closing pressure in the grapple actuator could optionally be combined with monitoring of the yawning position indication inorder to improve the operation of the grapple to save energy when performing the workflows of loading and un-loading logs.

[0083] Further, a reliance solely on either the pressure indication (inside the grapple actuator) or the yawning position indication is included in the inventive scope.

[0084] It should be noted that the hydraulic system, which provides hydraulic flow to the grapple actuator, typically includes one or several pressure sensors capable of monitoring pressure in the grapple actuator as long as the grapple valve is open. That pressure sensor could constitute the pressure sensor for providing the pressure indication of the hydraulic closing pressure of the grapple actuator, in case there it is not prioritized to sense the pressure inside of the grapple actuator.

[0085] Grapple yawning monitoring is used herein to monitor the amount of opening of the grapple, more particularly a separation of the claws of the grapple. A yawning position sensor (which could include several sensor units) could be located on the grapple actuator to sense the linear position thereof (or on each grapple actuator if the grapple claws require several actuators) or be located in connection to a rotational axis of each grapple claw.

[0086] Such sensor or sensors located on the grapple may require radio communication means or a wired connection fed through the grapple rotator to communicate with the controller.

Claims

CLAIMS1. A method of loading logs on a log-handing vehicle (1 ), said vehicle comprising:a frame (1A, 1 B), a propulsion system (7), and a log-carrying compartment (3) on top of the frame, said log-carrying compartment (3) being arranged to carry logs in a main direction,a controller (24) arranged to control a hydraulic system (20) of the vehicle, said hydraulic system comprising:an articulated crane (2) rotatably mounted at its base to the frame via a hydraulic crane rotator (2a), said crane having a grapple (4) attached at the tip of the crane via a hydraulic grapple rotator (2b),a hydraulic grapple actuator (4c) arranged to perform opening movement, closing movement, or stopped movement of the grapple (4),a pressure sensor (22) arranged to provide a pressure indication of a hydraulic closing pressure of the grapple actuator (4c),optionally, in case of grapple yawning monitoring, a yawning position sensor (26, 27) arranged to provide a yawning position indication of the grapple’s (4) current yawning position,a hydraulic pump system (12) and a hydraulic valve system (13, 13A, 13B), said hydraulic valve system having a grapple valve (18) arranged to control a hydraulic flow from the hydraulic pump system to the grapple actuator (4c) to control the grapple’s movements, said method being implemented in the controller (24) and said method comprising the steps of:controlling the grapple actuator (4c) to perform closing movement around a log by controlling the hydraulic flow through the grapple valve (18) to the grapple actuator and monitoring said pressure indication, and, in case of grapple yawning monitoring, in case of grapple yawning monitoring, monitoring said yawning position indication,when detecting that the closing pressure (P) has reached an upper pressure threshold value (P-thres 2), and / or, in case of grapple yawning monitoring, when detecting that the yawning position has become static, automatically controlling the grapple actuator (4c) to assume stopped movement by controlling the grapple valve (18) to shut to inhibit flow to the grapple actuator (4c),when detecting that the provided pressure indication has fallen below a lower pressure threshold value (P-thres 1), and / or, in case of grapple yawning monitoring, when detecting that the yawning position has changed by at least a predetermined opening amount or at least a predetermined closing amount, automatically controlling the grapple actuator toassume closing movement by controlling the grapple valve (18) to re-open to allow a hydraulic flow to the grapple actuator (4c) to close the grapple (4) around the log, lifting the grapple (4) by the articulated crane (2),when the grapple actuator (4c) has assumed stopped movement, providing from the pump system (12) a hydraulic flow at a hydraulic pressure less than the upper pressure threshold value (P-thres 2), via the valve system (13, 13A, 13B), to at least one of the grapple rotator (2b) and the crane rotator (2a),aligning the log with the main direction by the grapple rotator (2b) and the crane rotator (2a),lowering the grapple (4) by the articulated crane (2),controlling the grapple actuator (4c) to perform opening movement to release the log in the log-carrying compartment (3) by controlling the hydraulic flow through the grapple valve (18) to the grapple actuator (4c).

2. The method according to claim 1 , wherein the hydraulic flow provided to said at least one of the grapple rotator (2b) and the crane rotator (2a), when the grapple actuator (4c) has assumed stopped movement, is provided with a hydraulic pressure less than the lower pressure threshold value (P-thres 1).

3. The method according to any of the claims 1 - 2, wherein the lower pressure threshold value (P-thres 1 ) is less than 95% of the upper pressure threshold value (P-thres 2).

4. The method according to any of the claims 1 - 3 claims, further comprising, receiving in the controller (24) a command, on which to base the control movements of the grapple (4), said command being at least one of: a closing grapple command (CLOSE GRAPPLE = ON), an opening grapple command (OPEN GRAPPLE = ON), a stopping grapple command (CLOSE GRAPPLE = OFF), a closing grapple speed command, an opening grapple speed command.

5. The method according to claim 4, wherein the commands comprise, operator-input commands and / or system commands generated by a computer-implemented task manager.

6. The method according to claim 5, comprising when the closing grapple (4) command is being received in the controller, repeating the steps of,when detecting that the provided closing pressure (P) has reached the upper pressure threshold value (P-thres 2), automatically controlling the grapple actuator (4c) to assumestopped movement by controlling the grapple valve (18) to shut to inhibit flow to the grapple actuator (4c),when detecting that the provided pressure indication has fallen below the lower pressure threshold value (P-thres 1), automatically controlling the grapple actuator (4c) to assume closing movement by controlling the grapple valve (18) to re-open to allow a hydraulic flow to the grapple actuator (4c) to close the grapple around the log.

7. The method according to any of the preceding claims, wherein the pressure sensor (22) arranged to provide a pressure indication of a hydraulic closing pressure of the grapple actuator (4c) is connected to the grapple actuator and arranged to sense the hydraulic pressure therein.

8. Log-handling vehicle (1), comprising,a frame (1A, 1 B), a propulsion system (7), and a log-carrying compartment (3) on top of the frame, said log-carrying compartment (3) being arranged to carry logs in a main direction,a controller (24) arranged to control a hydraulic system (20) of the vehicle, said hydraulic system comprising,an articulated crane (2) rotatably mounted at its base to the frame via a hydraulic crane rotator (2a), said crane having a grapple (4) attached at its tip via a hydraulic grapple rotator (2b),a hydraulic grapple actuator (4c) arranged to perform opening movement, closing movement, or stopped movement of the grapple (4),a pressure sensor (22) arranged to provide a pressure indication of a hydraulic closing pressure (P) of the grapple actuator (4c),optionally, in case of grapple yawning monitoring, a yawning position sensor (26, 27) arranged to provide a yawning position indication of the grapple’s (4) current yawning positiona hydraulic pump system (12) and a hydraulic valve system (13, 13A, 13B), said hydraulic valve system having a grapple valve (18) arranged to control a hydraulic flow from the hydraulic pump system (12) to the grapple actuator (4c) to control the grapple’s movements,wherein the controller (24) is configured to,control the grapple actuator(4c) to perform closing movement around a log by controlling the hydraulic flow through the grapple valve (18) to the grapple actuator (4c) and monitoring said pressure indication and, in case of grapple yawning monitoring, in case of grapple yawning monitoring, monitoring said yawning position indication,when detecting that the provided closing pressure (P) has reached an upper pressure threshold value (P-thres 2), and / or, in case of grapple yawning monitoring, when detecting that the yawning position has become static, automatically control the grapple actuator to assume stopped movement by controlling the grapple valve (18) to shut to inhibit flow to the grapple actuator (4c),when detecting that the provided pressure indication has fallen below a lower pressure threshold value (P-thres 1), and / or, in case of grapple yawning monitoring, when detecting that the yawning position has changed by at least a predetermined opening amount or at least a predetermined closing amount, automatically control the grapple actuator (4c) to assume closing movement by controlling the grapple valve (18) to re-open to allow a hydraulic flow to the grapple actuator (4c) to close the grapple (4) around the log, lift the grapple (4) by the articulated crane (2),align the log with the main direction by the grapple rotator (2b) and the crane rotator (2a), when the grapple actuator (4c) has assumed stopped movement, provide from the pump system (12), via the valve system (13, 13A, 13B), a hydraulic flow at a hydraulic pressure, less than the upper pressure threshold value (P-thres 2), to at least one of the grapple rotator (2b) and the crane rotator (2a),lower the grapple (4) by the articulated crane (2),control the grapple actuator (4c) to perform opening movement to release the log in the log-carrying compartment by controlling the hydraulic flow through the grapple valve (18) to the grapple actuator (4).

9. The log- handling vehicle according to claim 8, wherein the hydraulic flow provided to said at least one of the grapple rotator (2b) and the crane rotator (2a), when the grapple actuator (4c) has assumed stopped movement, is provided with a hydraulic pressure less than the lower pressure threshold value (P-thres 1).

10. The log- handling vehicle according to any of the claims 8 - 9, further comprising an operator-input device arranged to provide operator-input commands to the controller (24) to render closing or stopped grapple movement, as long as actively maintained by the operator, wherein, optionally, the operator-input device further comprises a control lever (23a) for controlling at least one of the grapple rotator (2b) and the crane rotator (2a).

11. The log- handling vehicle according to claim 10, wherein on a side surface of the control lever (23a) is provided a control device (23b) which, through operator-input commands, allows switching between: a closing grapple command (CLOSE GRAPPLE = ON) , an opening grapple command (OPEN GRAPPLE = ON), a stopping grapple command(CLOSE GRAPPLE = OFF), and, optionally, a closing grapple speed command and an opening grapple speed command.

12. The log-handling vehicle according to claim 11 , wherein the side surface of the operatorinput device (23b) comprises a thumb button / three-way switch with spring-loaded return to center position for affecting the operator-input commands.

13. The log-handling vehicle according to any of the claims 8-12, wherein the hydraulic pump system (12) comprises at least one of the following combinations, a flow-controllable hydraulic pump (15) driven by an internal combustion engine (ICE), a fixed displacement hydraulic pump (15’) driven by a speed controllable electric motor (5’).

14. The log- handling vehicle according to any of the claims 8-13, wherein the log-handling vehicle is a one of, a cut-to-length-logging harvester vehicle and a log-forwarder vehicle, and wherein the hydraulic pump system (12) comprises a hydraulic pump (15) common to the grapple actuator (4c) and at least one of, the grapple rotator (2b), the crane rotator (2a), a main boom actuator (2c) between a crane base and a main boom of the articulated crane (2), a knuckle boom actuator (2d) between a main boom and a knuckle boom of the articulated crane, and a telescopic boom actuator of the knuckle boom of the articulated crane.

15. The log-handling vehicle according to claim 14, wherein the hydraulic system comprises first and second separable hydraulic valve groups, respectively, coupled via first and second hydraulic circuits, respectively, to the hydraulic pump system, wherein the first valve group provides hydraulic flow to the crane rotator (2a), the grapple rotator (2b), and the telescopic boom actuator (2c) of the knuckle boom of the articulated crane and wherein the second valve group provides hydraulic flow to the grapple actuator (4c), the main boom actuator (2d) between a crane base and a main boom (2e) of the articulated crane, and the knuckle boom actuator (2d) between a main boom and a knuckle boom of the articulated crane.

16. The log-handling vehicle according to any of the claims 8-15, wherein the log-handling vehicle (1) is configured allow the automatic controlling of the grapple actuator (4c) occur predominantly during a log-loading sequence comprising a first closing of the grapple (4) around the log, manipulations of the log by the articulated crane (2), and a first releasing of the log aligned in the main direction in the log-carrying compartment (3).

17. The log-handling vehicle according to any of the claims 8 - 16, wherein the pressure sensor (22) arranged to provide a pressure indication of a hydraulic closing pressure of the grapple actuator (4c) is connected to the grapple actuator and arranged to sense the hydraulic pressure therein.

Images