Patent Application
20230264926
The present invention relates to a timber handling vehicle according to the pre-amble of claim 1. The invention also relates to a timber grip according to claim 13.
In timber handling vehicles, an operator primarily uses a combination of two hydraulically manoeuvrable units, namely a crane and a timber grip for timber handling at a load compartment constituent in the timber handling vehicle. By means of the timber grip, a bundle of timber is localized, collected, captured and gripped with strong force with the grip hooks operating in pairs and comprised in the timber grip, whereby timber is loaded onto the load compartment of the timber handling vehicle as well as unloaded from same. Consequently, said crane and timber grip consume most of the hydraulic flow generated by a pump constituent in the vehicle during work. As a result, the operator of the vehicle may experience that the timber grip does not in a distinct manner respond to the operators control command or that the timber grip has very long response times at closure and therefore does not grip around the timber in a fast and efficient manner, in particular if the crane is manoeuvred at the same time. This phenomenon, which is usually termed “puncturing” within hydraulics, means that the hydraulic pump that is comprised in the hydraulic system of the vehicle, via a control valve and pipes for the respective consumers, can only supply limited power to the respective consumers.
The power that is transferred in a hydraulic system is defined by the fluid pressure (N/m2) multiplied by the volume flow (m3/second). Due to long pipes over the crane and further to the timber grip that is attached at the farthest crane end, energy losses occur, in particular if the outermost knuckle-boom is also telescopically extendable. Long pipes also imply that the flow is limited and that power losses occur, which reduces the manoeuvrability of the timber grip in a manner that may not only be experienced as disturbing by the operator, but also affects the operators possibility of carrying out work with the timber grip at the load compartment in an efficient way. In the following, the term timber does not only refer to wood that is intended for sawing, but for example also forest waste, pulpwood and the like, which is to be handled correspondingly.
To solve this problem, it has been decided in prior art timber handling vehicles to minimize the problem of energy losses over the crane by over dimensioning the pump capacity of the hydraulic system somewhat and/or use hydraulic control valves of the proportional type and of the type that does not open fully, but only allows a limited amount of the flow, for example 75-80%, to pass through the valve to the consumer, whereby the remaining 20-25% of the flow is reserved for the other consumers. However, these measures are not only costly, but they also contribute to energy losses and unnecessary heat generation in the hydraulic system.
Consequently, there is a need for a timber handling vehicle that solves this problem and enables an operator to obtain “power as required” or makes it possible to adaptively adjust the power requirement by means of smart energy regulation of the hydraulic flow of the system in order to do the job of handling timber at a load compartment of a timber handling vehicle more efficiently.
A first object of the present invention is thus to obtain a timber handling vehicle that makes it possible to handle timber with timber grips at a load compartment more efficiently. A second object of the invention is to obtain a timber handling vehicle that can adapt the response of the timber grip to the operators control command, so that the work movements of the timber grip in the desired way correspond to the power requirement of the various work steps comprised by timber handling work at a load compartment, namely a first work step wherein the timber is localized, a second step in which the timber is collected by means of the grip hooks of the timber grip, a third work step whereby the collected timber is gripped via grabbing by the grip hooks of the timber grip against the timber. A third object of the invention is to offer smooth and for an operator virtually imperceptible start and stop functions in transitions between various operating modes of the timber grip in timber handling work.
According to a first embodiment of the invention, the hydraulic system of the timber handling vehicle includes a third pipe, which results in a regenerative fluid flow from the minus side to the plus side of the hydraulic cylinder, a valve means, which is arranged to the second pipe, and which valve means is configured to; drive in a first operating condition, where the valve means is closed and fluid flow from the minus side to the plus side of the hydraulic cylinder is directed via said third pipe, receive a pressure indication that indicates a pump feed pressure on the plus side of the hydraulic cylinder, determine whether the pump feed pressure is above a first operating condition threshold value and, if so, drive in a second operating condition, where the valve means is open, and fluid flow from the minus side of the hydraulic cylinder is directed to the tank.
According to a second embodiment of the invention, the valve means of the timber handling vehicle is further configured to; determine whether the pump feed pressure on the plus side of the hydraulic cylinder exceeds the first operating condition threshold value, but falls below a second operating condition threshold value, and, if so, vary the degree of opening in an intermediate transition area, where the fluid flow from the minus side to the plus side of the hydraulic cylinder at a predetermined regulation characteristic is gradually reduced as the pump feed pressure increases on the plus side of the hydraulic cylinder.
According to a third embodiment of the invention, the valve means of the timber handling vehicle is further configured to; determine whether the pump feed pressure on the plus side of the hydraulic cylinder exceeds the second operating condition threshold value, and, if so, drive in a third operating condition wherein the valve means is completely open and all fluid flow from the minus side of the hydraulic cylinder is directed to the tank.
According to a fourth embodiment of the invention, the valve means of the timber handling vehicle is configured so that a gradual transition between a first operating condition threshold value and a second operating conditions threshold value can be arranged at varying degree and gradually be reduced by regenerative operating duration or regenerative operating time.
According to a fifth embodiment a valve means included in the invention can be configured with a relatively long regenerative operating duration, where a gradual transition from the first to the second operating condition threshold value graphically forms a negative gradient, whose angular coefficient is calculated as a ratio for the pump pressure between the first and the second operating condition threshold value, respectively. According to the invention, said ratio should be below 0.5 (<0.5) for the transition not to have a negative effect on the operators driving experience.
In a preferred embodiment of the invention, the ratio for the regenerative operating duration can be in the 0.3-0.1 interval.
In the following, the invention is described in detail with reference to the accompanying drawings, in which;
The timber handling vehicle 1 includes a front 1A respectively rear 1B vehicle unit, which is articulately joined via a steering joint 1C. On its respective chassis, the front vehicle unit 1A carries a superstructure, mainly comprising a drive motor 5, a drivers cabin 6 and a hydraulic system 11, while the rear vehicle unit 1B carries a superstructure, mainly comprising said crane 2 and said load compartment 3 for timber 9. At the free end of the crane 2, said timber grip 4 is pivotably suspended via an articulation 10.
For positioning of the boom-tip and thereby the timber grip 4, the crane 2 comprises both a supporting body 2a or pillar, with which a lifting arm 2b is articulated, with which in turn a knuckle-boom 2c is articulated, which in turn may comprise a number of telescopic projections 2d for increasing the range. For swinging laterally, the crane body 2a is pivotably accommodated in a crane foot, which is attached in the chassis of the rear vehicle unit 1B. The respective parts of the crane 2 are pivotable in height by means of hydraulic cylinders, which are supplied with hydraulic fluid via hoses or pipes, which normally extend through the body and associated crane parts. The crane body 2a includes a toothed rim, which for swinging of the crane 2 at a horizontal plane on the rear vehicle unit 1B is affected by a hydraulic motor (not shown) equipped with a toothed rim.
As most clearly appears from
Referring to
In an alternative embodiment of the invention, said components could be integrated as part of the double-acting hydraulic cylinder 4c of the timber grip. An example of such embodiment can be seen in more detail if the detail enlargement in
The hydraulic system 11, 12 includes a pressure medium source in the form of a pump 15 that is driven by said drive motor 5 and sucks the hydraulic fluid from a tank 16, which fluid feeds a pressure pipe 17. The pressure pipe 17 is connected with a control valve 18 operable by an operator of the four-way three-state valve type for distribution of the hydraulic fluid to the hydraulic cylinder 4c of the timber grip 4 for actuating the grip hooks 4a, 4b of the timber grip. Said control valve 18 is included in the valve block (not shown) accommodated in the front vehicle unit 1A of the timber handling vehicle 1.
Depending on the set state, the control valve 18 can thus selectively deliver a pressurized fluid flow to a plus side 15:1 of the hydraulic cylinder 4c via a first pipe 15A connected to the hydraulic cylinder respectively to a minus side 15:2 of the hydraulic cylinder 4c via a second pipe 15B connected to the hydraulic cylinder. In the following, the plus side 15:1 means the hydraulic cylinders 4c first pressure space, which has a larger area, and the minus side 15:2 is the hydraulic cylinders second smaller pressure space, though which a piston rod extends included in the hydraulic cylinder 4c.
In the field 12, 15C denotes a third pipe forming a by-pass with which hydraulic fluid, according to the invention, can be regenerated by flowing directly from the minus side 15:2 of the hydraulic cylinder to its plus side 15:1 instead of taking a detour via the tank 16. A first non-return valve is denoted 20, which is arranged to said third pipe 15C in order to restrain a fluid flow from the plus side 15:1 of the hydraulic cylinder 4c to the minus side 15:2 and further on to the tank 16. A valve means denoted 21 is arranged to the second pipe 15B.
According to the invention, the valve means 21 is configured to drive the hydraulic system in a first operating condition, wherein the valve means is closed and the fluid flow from the hydraulic cylinders 4c minus side 15:2 to the plus side 15:1 is directed via said third pipe 15C. The valve means 21 is pressure-sensing and via a first pilot pipe 21:1, it is arranged to receive a pressure indication, indicating a pump feed pressure P on the plus side 15:1 of the hydraulic cylinder 4c and to determine, whether the pump feed pressure P is above a first operating condition threshold value Z1 (see also
Furthermore, the valve means 21 can also be configured to determine whether the pump feed pressure P on the plus side 15:1 of the hydraulic cylinder 4c exceeds the first operating condition threshold value Z1, but is below a second operating condition threshold value Z2, and, if so, vary the degree of opening in an intermediate transition area, wherein the fluid flow from the minus side 15:2 to the plus side 15:1 of the hydraulic cylinder at a predetermined regulation characteristic at a predetermined duration is gradually reduced as a consequence of a negative gradient as the pump feed pressure P increases on the plus side 15:1 of the hydraulic cylinder 4c (see also
According to the invention, the pressure-sensing valve means 21 is configured to be arranged at varying degree of longer or shorter duration by beforehand configuring the regulation characteristic of the valve means in the form of a negatively decreasing curve or a negative gradient as a downwardly inclined straight line between said first and second operating condition threshold values Z1, Z2.
On closer review of the negative gradient in the diagram in
According to the invention, the valve means 21 can be configured to provide a relatively long regenerative operating duration RD, where a gradual transition from the first operating condition threshold value Z1 and the second operating condition threshold value Z2 graphically forms a negatively decreasing curve or gradient, whose regenerative operating duration RD is controlled by an angular coefficient selected for the gradient calculated as a ratio (Z1/Z2) between the first operating condition threshold value Z1 and the second operating condition threshold value Z2. According to the invention, said ratio should be below 0.5 (<0.5) for the transition not to have a negative effect on the operators driving experience and work capacity at timber handling. In a preferred embodiment of the invention, the ratio (Z1/Z2) between the first operating condition threshold value Z1 and the second operating condition threshold value Z2 for the regenerative operating duration RD can be in the 0.3-0.1 interval.
In an embodiment of the invention shown in
In a timber vehicle according to the present invention, it has proven suitable to select a ratio for an alternating pressure at the pump pressure P between the first operating condition threshold value Z1 and the second operating condition threshold value Z2, i.e. (Z1/Z2), which is below ½ and preferably is in the ⅓-¼ range or the ⅓- 1/10 range.
The valve means 21 can further be configured to determine whether the pump feed pressure P on the plus side 15:1 of the hydraulic cylinder 4c exceeds the second operating condition threshold value Z2, and, if so, drive in a third operating condition wherein the valve means 21 is completely open and substantially all fluid flow from the minus side 15:2 of the hydraulic cylinder 4c is directed to the tank 16. In this state, the hydraulic system 11, 12 works in the conventional manner without regeneration. Thus, the regeneration degree is zero.
In an embodiment of the invention, the valve means 21 can include an adjustable (variable) valve means 21 of the pressure-sensing type, which via said pilot pipe 21:1 is sensitive to a pump feed pressure P on the hydraulic cylinders 4c plus side, wherein the indicated amount of fluid flow from the hydraulic cylinders 4c minus side 15:2 to the plus side 15:1 is automatically regulated through the degree of opening of the valve means (21), in which the valve means 21 is configured to direct all fluid flow (100% regeneration) from the hydraulic cylinders 4c minus side 15:2 to the plus side 15:1, when the hydraulic cylinder 4c operates at a pressure on the plus side, which is below a predetermined first operating condition threshold value Z1 (see also
As appears from the hydraulic scheme in
In an alternative embodiment of the invention, said adjustable and pressure-sensing valve means 21 can be constituted by a three-port load-holding valve of the pilot type with integrated non-return valve and drainage to avoid the problems with counter-pressure mentioned above. In this context, it should be understood that the pump pressure P on the hydraulic cylinders 4c plus side 15:1 controls the degree of opening of the current load-holding valve. In yet another alternative embodiment, said load-holding valve 21 can be provided with variable regulation characteristic. The load-holding valve 21 can advantageously be of a balanced execution to be able to control the movement in a manner that rather corresponds to a more advanced PWM-pulse controlled proportional valve.
Localization of Timber
In a first work step, the timber grip 4 “runs empty” in which step, the timber 9 in the load compartment 2 is localized. The grip hooks 4a, 4b of the timber grip 4 here pivot separately to a timber-receiving state, wherein the hydraulic cylinder 4c is in its shortest compressed state with the piston at a bottom state. The minus chamber 15:2 of the hydraulic cylinder 4c is thus completely filled with fluid, while the plus chamber 15:1 is emptied for fluid contents, which should be realized if the schematically shown hydraulic cylinder in
Collection of Timber
In a second work step, the operator begins to close the timber grip 4. As long as the pump pressure P on the hydraulic cylinders 4c plus side 15:1 is lower than the alternating pressure, i.e. P<Z1, the timber grip 4 function is 100% regenerative, wherein the grip 4, due to the differential piston principle and because both chambers 15:1, 15:2 of the hydraulic cylinder 4c are pressurized, the piston of the hydraulic cylinder and thus the timber grip hooks 4a, 4b will move at fast pace, but at lower force due to the differential relationship as long as the piston is substantially unloaded. Consequently, all fluid is directed from the hydraulic cylinders 4c minus side 15:2 to the plus side 15:1 via the third pipe 15C and the non-return valve 20. No flow is directed via the second pipe 15B back to the tank 16.
Contact with and Capture of Timber
In this third work step, the timber grip 4 begins to move timber 9 from the sides of the load compartment 9 and further in towards the central middle of the timber grip. The pump pressure P on the hydraulic cylinders 4c plus side 15:1 is still below the alternating pressure Z1, and the function is 100% regenerative, wherein the timber grip 4 grip hooks 4a, 4b move towards each other at fast pace.
Gripping the Timber—Start Reducing
In the fourth work step, the timber grip 4 has collected sufficient timber 9 for the load to result in the pump pressure P on the hydraulic cylinders 4c plus side 15:1 to exceed the alternative pressure Z1. The valve means 21 ensures that the second pipe 15B, i.e. the return pipe to the tank 16 opens proportionally by the valve means' 21 first pilot pipe 21:1 on the plus side 15:1 beginning to become pressurized. The fluid flow in the second pipe 15B (the return pipe) increases successively concurrently with the fluid flow over the third pipe 15C and the non-return valve 20 decreasing correspondingly. The speed of the function decreases correspondingly. Due to the long transition area between the duration limits defined between the first operating condition threshold value Z1 and the second operating condition threshold value Z2 according to the invention, the operator will in practice not notice the speed reduction of the timber grip 4 when it alternates between said respective operating states. Due to the valve means 21 being variable, it is possible to vary the duration limits and thus choose a gradual transition and desired angular coefficient for the negative gradient with shorter or longer duration between both alternating pressures Z1, Z2, which is illustrated graphically in the diagram in
End of Transition—Double-Acting
The pump pressure P on the hydraulic cylinders 4 plus side 15:1 has obtained a predetermined setting pressure Z2. The valve means 21 is completely open and no flow runs via the third pipe 15C and the non-return valve 2. The speed of the piston and hence the timber grip 4 at grip movement has reduced the piston area ratio correspondingly. The area against which the pump pressure P acts, corresponds to the entire area of the piston.
Gripping the Timber with Holding Force
The grip movement of the timber grip 4 is completed, whereby the maximum pump pressure Pmax for the function has been obtained. The timber 9 is thus held at full holding force in the timber grip 4.
Opening of the Timber Grip—Minus Stroke
Through switching of the control valve 18, the pump pressure P is directed out into the second pipe 15B, whereby the hydraulic cylinders 4 minus side 15:2 is pressurized concurrently with the plus side 15:1 being connected to the tank 16. The fluid flow is prevented from flowing from the hydraulic cylinders 4c minus side 15:2 to the plus side 15:1 by pressurization of the non-return valve's 20 pilot pipe 20:1 from the minus side. At the hydraulic cylinders 4 minus stroke, fluid flows past the valve means 21 via the parallel non-return valve function 22.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2050966-7 | Aug 2020 | SE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/SE2021/050798 | 8/17/2021 | WO |
