Control circuit for a harvester head

Abstract

A control circuit (10) for a feed device (9) in a head (4) of a harvester and a method in the control circuit (10). The control circuit (10) comprises a valve arrangement (11) arranged at a tank line (TL) to sense a pressure in at least one input of at least one motor (M1, M2, M3, M4), to detect a pressure drop in the at least one input of the at least one motor (M1, M2, M3, M4), and to generate an increase in the pressure in the tank line (TL) in response to the sensed pressure drop in the at least one input of the at least one motor (M1, M2, M3, M4) to cause a replacement flow of pressure fluid into the at least one input of the at least one motor (M1, M2, M3, M4) through the tank line (TL).

Description

Technical Field

[0001] The present invention relates to a control circuit for a feed device in the head of a harvester and a method for controlling the control circuit for the feed device in the head of a harvester. Background Technology

[0002] A logging machine is a forestry machine that can move across terrain and cut down upright trees and cross-cut them into sections of the desired length. A logging machine includes a logging head that provides the tools for the logging machine, through which the logging machine can clamp upright trees and cut and fell them, as well as remove branches from fallen trees and cross-cut them into sections of the desired length.

[0003] The logging head includes a feeding device for pulling or traction of fallen trees through the logging head. The feeding device includes multiple feeding components (e.g., feed wheels) that press against the trunk of the tree and, when the feeding components are operated, move the tree through the logging head.

[0004] The logging head is typically hydraulically operated, thus including a hydraulically operated control circuit for controlling the operation of the feed mechanism. The control circuit for the feed mechanism typically includes multiple hydraulic motors arranged to operate multiple feed members such that the feed members can be operated forward to move the tree forward through the logging head, and, if necessary, backward to move the tree backward within the logging head.

[0005] The feeding components are typically arranged in two groups: an upper feeding group and a lower feeding group. The corresponding hydraulic motors are then also divided into corresponding groups: an upper hydraulic motor group and a lower hydraulic motor group. The hydraulic motors in each group are arranged in parallel with each other, and the hydraulic motors in one group are arranged in series with respect to one motor in the other group. Thus, when the feeding device is operated, the pressurized fluid operating the hydraulic motors flows from one motor in one group to one motor in the other group, the direction of the pressurized fluid flow depending on whether the tree is to move forward or backward in the head of the harvester.

[0006] In the head of a logging machine, a situation may arise where one of the feed components has a good grip on the tree trunk, but other feed components slide relative to the trunk, rendering the tree immobile. This can lead to insufficient pressurized fluid flow on the suction side of at least one of the hydraulic motors, which in turn can cause cavitation in that motor.

[0007] EP Publication 2724611B1 discloses a solution for avoiding cavitation in the control circuit of a feed device. In the solution of EP Publication 2724611B1, a valve assembly is connected to a pressure line in the control circuit of the feed device to attempt to maintain sufficient pressure on the suction side of the hydraulic motor by actively supplying pressurized fluid to the hydraulic motor. The solution disclosed in EP Publication 2724611B1 is quite complex, but it still cannot prevent cavitation when feeding trees forward through the head of the harvester.

[0008] Therefore, an alternative solution is needed to avoid cavitation in the control loop of the feed device at the head of the harvester. Summary of the Invention

[0009] The purpose of this invention is to provide a novel control loop for a feed device in the head of a logging machine and a novel method for controlling the control loop of the feed device in the head of a logging machine.

[0010] The invention is characterized by the features of the independent claims.

[0011] The present invention is based on the concept of arranging valve devices in a tank line to sense the dominant pressure in the control loop to detect the tendency of possible cavitation to begin in some volumes in the control loop, and in response to the sensed pressure indicating the initiation of possible cavitation in some volumes of the control loop, increasing the dominant pressure in the tank line to supply a replacement flow of pressurized fluid to fill the volume.

[0012] The disclosed solution is relatively simple to avoid cavitation in the control loop, requiring only some additional valves without any modification to the basic structure of the control loop.

[0013] Some embodiments of the present invention are disclosed in the dependent claims. Attached Figure Description

[0014] The present invention will now be described in more detail with reference to the accompanying drawings, in which:

[0015] Figure 1 The logging machine is shown schematically;

[0016] Figure 2 An end view of the head of a logging machine is shown schematically;

[0017] Figure 3 An embodiment of a control loop for controlling the operation of the feed device in the head of a logging machine is schematically shown;

[0018] Figure 4A second embodiment of the control loop for controlling the operation of the feed device in the head of a harvester is schematically shown;

[0019] Figure 5 A third embodiment of a control loop for controlling the operation of the feed device in the head of a harvester is schematically shown; and

[0020] Figure 6 Exemplary measurements illustrating the operation of an embodiment of the control loop are schematically shown, and

[0021] Figure 7 A prior art control loop for controlling the operation of the feed device in the head of a logging machine is schematically shown.

[0022] For clarity, the accompanying drawings illustrate some embodiments of the invention in a simplified manner. The same reference numerals denote the same elements in the drawings. Detailed Implementation

[0023] Figure 1 A logging machine 1 is schematically shown. The logging machine 1 is a forestry machine that can move across terrain and fell upright trees and cut them crosswise into segments of desired length. The logging machine 1 includes a crane 2, which is connected to the logging machine 1 via a joint 3, allowing the crane 2 to rotate around the logging machine 1. A logging machine head 4 is located at the distal end of the crane 2.

[0024] The logging head 4 includes a joint 5, through which the logging head 4 is attached to the distal end of the crane 2 of the logging machine 1. The logging head 4 provides the tools of the logging machine 1, through which the logging machine 1 can clamp and cut and fell upright trees, as well as remove branches from fallen trees and cut them crosswise into segments of the desired length.

[0025] The logging head 4 includes, for example, a debranching device and a feeding device, wherein the debranching device is arranged to remove branches from the fallen tree as it is fed forward through the logging head 4 by means of the feeding device, i.e., arranged to cut the branches of the fallen tree. The logging head 4 also includes a cross-cutting device (e.g., a chainsaw) for cross-cutting the debranched tree into segments of the desired length. To achieve the above operations, the logging head 4 includes corresponding actuators, which include, for example, a set of typically hydraulically operated motors and cylinders. The operation of these actuators is typically controlled by a set of valves intended to control the flow rate of pressurized fluid (which is typically hydraulic oil) in the control circuit of the corresponding device.

[0026] Figure 2A highly schematic end view of the harvester head 4 is shown without any joint 5 shown. The harvester head 4 can be attached to the crane 2 of the harvester 1 via the joint 5. The harvester head 4 includes a main frame 6 and two sub-frames (i.e., a first sub-frame 7a and a second sub-frame 7b), which are connected to the main frame 6 on opposite sides of the main frame 6 via joints not shown, whereby the sub-frames 7a and 7b can rotate relative to the main frame 6. Figure 2 The machine head 4 is positioned as shown in the closed position and rotates to the open position along the path schematically indicated by arrow TD. In the open position of subframes 7a and 7b, the harvester head 4 can clamp the upright or fallen tree 8 to be processed next, and in the closed position of subframes 7a and 7b, the harvester head 4 can feed the fallen tree 8 through the harvester head and simultaneously remove the branches of the tree 8 and cut it crosswise into segments of the required length.

[0027] Figure 2 The diagram also schematically illustrates a feed device 9 intended to feed the fallen tree 8 through the head 4 of the harvester. The feed device 9 includes a set of feed components. Figure 2 In this embodiment, there are a total of four feed members FM1, FM2, FM3, and FM4. These feed members are intended to support the trunk of the tree 8 to be processed and to pull the tree 8 through the harvester head 4 during operation of the harvester head 4. The first feed member FM1 and the second feed member FM2 are arranged substantially parallel to the main frame 6 at the distance between them. The third feed member FM3 is arranged to the first sub-frame 7a, and the fourth feed member FM4 is arranged to the second sub-frame 7b. When the sub-frames 7a and 7b are in their closed positions, the third feed member FM3 and the fourth feed member FM4 are substantially parallel to each other at the distance between them, so that the first feed member FM1 and the second feed member FM2 are pressed against the trunk of the tree 8 substantially on opposite sides of the trunk of the tree 8 relative to the third feed member FM3 and the fourth feed member FM4.

[0028] exist Figure 2 In this embodiment, the feed components FM1, FM2, FM3, and FM4 are implemented as toothed feed wheels. However, one or more of the feed components FM1, FM2, FM3, and FM4 can also be implemented, for example, by feed rollers or annular tracks, or by some other means adapted to press against the trunk of the tree to traction or pull the tree through the head 4 of the harvester. The number of feed components and their relative positions can also be related to... Figure 2 The number of feed members and their relative positions are different in the illustrative embodiments disclosed.

[0029] The following reference Figure 7The general structure and operation of the hydraulically operable control loop 10 are discussed, wherein the disclosed solution can be applied to control the operation of the feed device 9 in the harvester head 4 of the harvester 1. The pressure fluid used in the control loop 10 can be any fluid that is substantially incompressible under pressure, and is preferably corrosion-resistant, such as hydraulic oil, and preferably biodegradable oil.

[0030] Control loop 10 includes a first hydraulic motor M1, which may be a motor arranged to operate a first feed member FM1. Control loop 10 also includes a second hydraulic motor M2, which may be a motor arranged to operate a second feed member FM2. When considering the flow of pressurized fluid in control loop 10, the first motor M1 and the second motor M2 are connected in parallel with respect to each other in control loop 10. Furthermore, the first motor M1 and the second motor M2 can be mechanically connected to each other via a shaft S, which forces the first motor M1 and the second motor M2 to operate synchronously with respect to each other.

[0031] The first feed member FM1 and the second feed member FM2, which are supported to the main frame 6 of the harvester head 4, can also be referred to as upper feed members, thus forming a set of upper feed members. The corresponding first motor M1 and second motor M2 that operate the first feed member FM1 and the second feed member FM2 can also be referred to as upper motors, thus forming a set of upper motors.

[0032] Furthermore, control circuit 10 includes a third hydraulic motor M3 and a fourth hydraulic motor M4. The third hydraulic motor M3 may be a motor arranged to operate a third feed member FM3, and the fourth hydraulic motor M4 may be a motor arranged to operate a fourth feed member FM4. When considering the flow of pressurized fluid in control circuit 10, the third motor M3 and the fourth motor M4 are connected in parallel with each other in control circuit 10.

[0033] The third feed member FM3 and the fourth feed member FM4, which are respectively supported to the first subframe 7a and the second subframe 7b of the harvester head 4, can also be referred to as lower feed members, thus forming a set of lower feed members. The corresponding third motor M3 and fourth motor M4 that operate the third feed member FM3 and the fourth feed member FM4 can also be referred to as lower motors, thus forming a set of lower motors.

[0034] When considering the flow of pressurized fluid in control loop 10, the first motor M1 and the third motor M3 are connected in series with respect to each other, such that a first intermediate volume V1 exists between the first motor M1 and the third motor M3. The first intermediate volume V1 is the connecting volume between the first motor M1 and the third motor M3, providing a flow path for the pressurized fluid flow between the first motor M1 and the third motor M3. Similarly, when considering the flow of pressurized fluid in control loop 10, the second motor M2 and the fourth motor M4 are connected in series with respect to each other, such that a second intermediate volume V2 exists between the second motor M2 and the fourth motor M4. The second intermediate volume V2 is the connecting volume between the second motor M2 and the fourth motor M4, providing a flow path for the pressurized fluid flow between the second motor M2 and the fourth motor M4.

[0035] Figure 7 In this embodiment, motors M1, M2, M3, and M4 have fixed volumes and are two-directional (i.e., these motors can operate in two opposite directions) and include an input that can receive or discharge pressurized fluid flow depending on the primary operating direction of the motor. The operating direction of motors M1, M2, M3, and M4 is controlled by a directional control valve DCV. Figure 7 In this embodiment, the directional control valve DCV is a 4-way 3-position valve. The directional control valve DCV is connected to the first motor M1 and the second motor M2 via a first connecting line CL1, and to the third motor M3 and the fourth motor M4 via a second connecting line CL2. The first connecting line CL1 and the second connecting line CL2, together with the pressure line PL (discussed in more detail in the next paragraph), provide a pressure line system arranged to deliver pressurized fluid flow to the motors M1, M2, M3, and M4.

[0036] The pressurized fluid flow for operating motors M1, M2, M3, and M4 is supplied by hydraulic pump PU through pressure line PL and directional control valve DCV. Figure 7 In this implementation, the hydraulic pump PU is unidirectional (i.e., it can only operate in one direction) and has an adjustable volume. For clarity, in Figure 7 The motor used to operate pump PU is not disclosed. The return flow of pressurized fluid from motors M1, M2, M3, and M4 is supplied to tank TK in control loop 10 via directional control valve DCV and tank line TL.

[0037] Figure 7The control loop 10 also includes a first pressure relief component PR-AC1 with an anti-cavitation valve between the tank line TL and the first intermediate volume V1, and a second pressure relief component PR-AC2 with an anti-cavitation valve between the tank line TL and the second intermediate volume V2. The purpose of the first anti-cavitation valve PR-AC1 and the second anti-cavitation valve PR-AC2 is to protect the equipment in the control loop 10 from overpressure or pressure spikes that may occur in the control loop 10 when motors M1, M2, M3, and M4 are operated. Furthermore, the purpose of these first pressure relief components PR-AC1 and second pressure relief components PR-AC2 with anti-cavitation valves is to maintain a sufficient pressure level in the first intermediate volume V1 and the second intermediate volume V2 in the event that some of the motors M1, M2, M3, and M4 tend to begin cavitation due to insufficient pressure fluid flow through the corresponding intermediate volumes V1 and V2.

[0038] The control loop 10 also includes a third pressure relief component PR-AC3 with an anti-cavitation valve and a fourth pressure relief component PR-AC4 with an anti-cavitation valve, to also protect the equipment in the control loop 10 from overpressure or pressure spikes that may occur in the control loop 10 when motors M1, M2, M3, and M4 are operated. The third pressure relief component PR-AC3 and the fourth pressure relief component PR-AC4 with anti-cavitation valves are also equipped with anti-cavitation functions to prevent cavitation from occurring at the ports of the directional control valve DCV to which the first connecting line CL1 and the second connecting line CL2 are connected, in response to a rapid change in the operating direction of the motors, which could initiate cavitation at the directional control valve DCV.

[0039] Figure 7 The control loop 10 also includes a check valve CV between the directional control valve DCV and the tank TK, which is used to provide some pressure in the tank line TL to prevent completely uncontrollable pressure fluid flow in the tank line TL.

[0040] The basic operation of control loop 10 is as follows.

[0041] When tree 8 is advanced through the harvester head 4 for pruning and cross-cutting, the directional control valve DCV is in the first operating position, schematically indicated by reference numeral P1. This allows pump PU to supply pressurized fluid from tank TK through pressure line PL, ports P and A in the directional control valve DCV, and the first connecting line CL1 to the first motor M1 and the second motor M2, supplying substantially equal amounts to both motors. Pressurized fluid flows from the first motor M1 through the first intermediate volume V1 into the third motor M3, and pressurized fluid flows from the second motor M2 through the second intermediate volume V2 into the fourth motor M4. Figure 7As schematically shown in the embodiment, if the first motor M1 and the second motor M2 are mechanically connected to each other via shaft S, the first motor M1 and the second motor M2 operate synchronously relative to each other. This has the effect of operating the corresponding feed members FM1, FM2 synchronously as well, and of generating substantially equal distribution of pressure fluid flow from the first motor M1 and the second motor M2 through the corresponding intermediate volumes V1, V2 to the third motor M3 and the fourth motor M4, so that the tree 8 is fed through the harvester head 4 as well as possible. Thus, all the feed members FM1, FM2, FM3, FM4 pull the tree 8 through the harvester head 4 at substantially the same speed, regardless of the clamping of the feed members.

[0042] Furthermore, pressurized fluid flows from the third motor M3 back to the tank TK via the second connecting line CL2, ports B and T in the directional control valve DCV, and the tank line TL. Similarly, pressurized fluid flows from the fourth motor M4 back to the tank TK via the second connecting line CL2, ports B and T in the directional control valve DCV, and the tank line TL.

[0043] When tree 8 is fed backward in the head of the harvester 4 for some reason, the directional control valve DCV is in the third operating position, schematically indicated by reference numeral P3. Pump PU then supplies pressurized fluid from tank TK to the third motor M3 and the fourth motor M4 through pressure line PL, ports P and B of the directional control valve DCV, and the second connecting line CL2, supplying substantially equal amounts to both motors. Pressurized fluid flows from the third motor M3 through the first intermediate volume V1 into the first motor M1, and from the first motor M1 back to tank TK through the first connecting line CL1, ports A and T of the directional control valve DCV, and tank line TL. Pressurized fluid flows from the fourth motor M4 through the second intermediate volume V2 into the second motor M2, and from the second motor M2 back to tank TK through the first connecting line CL1, ports A and T of the directional control valve DCV, and tank line TL.

[0044] If an overpressure or pressure spike occurs in the protection zone of at least one of the pressure relief components PR-AC1, PR-AC2, PR-AC3, PR-AC4 with anti-cavitation valves, then the corresponding pressure relief component PR-AC1, PR-AC2, PR-AC3, PR-AC4 with anti-cavitation valves can open the connection to the tank line TL and further to the tank TK to limit the pressure in the control loop 10.

[0045] When the feed device 9 is idle, the directional control valve DCV is in the second operating position, schematically indicated by the reference numeral P2 in the attached drawing. Figure 7The control loop 10 is presented under this operating condition, in which no intentional pressure fluid flow occurs.

[0046] Any potential leakage from any of the motors M1, M2, M3, and M4 is directed from the motor housing to the housing TK via the corresponding drain line DR. Motors M1, M2, M3, and M4 can be implemented, for example, by a radial piston motor, but other suitable motors may also be used.

[0047] Under normal operating conditions, when the tree 8 is fed forward through the head of the harvester 4, the first pressure relief component PR-AC1 and the second pressure relief component PR-AC2 with anti-cavitation valves are usually not activated because the first motor M1 and the second motor M2 generate substantially equal distribution of pressure fluid flow, wherein a sufficient amount of pressure fluid flow to the third motor M3 and the fourth motor M4 prevents cavitation from occurring at the input ports of the third motor M3 and the fourth motor M4.

[0048] If the tree 8 is fed backwards, the operating conditions are significantly different from those for forward feeding. In this case, because there is no mechanical connection between the third motor M3 and the fourth motor M4, there is no distribution of pressurized fluid flow from the third motor M3 and the fourth motor M4 to the first motor M1 and the second motor M2. Therefore, cavitation may occur at the input ports of either the first motor M1 or the second motor M2. An example of such an operation is that the third feed member FM3, operated by the third motor M3, provides good gripping of the tree 8, but the first feed members FM1, the second feed member FM2, and the fourth feed member FM4, operated by the corresponding first motor M1, second motor M2, and fourth motor M4, provide poor gripping of the tree 8, and the tree 8 may become stuck in the harvester head 4 due to some branches. From the perspective of the control loop 10, in this operating condition, all pressurized fluid flow through port B of the directional control valve DCV flows through the fourth motor M4 to the second motor M2. Because the first motor M1 and the second motor M2 are mechanically connected to each other, the operation of the second motor M2 also causes the first motor M1 to operate. However, because the third motor M3 is not operating, the first motor M1 does not receive pressurized fluid flow from the third motor M3 and begins to cavitate. In this situation, the first pressure relief unit PR-AC1 with an anti-cavitation valve should provide a replacement flow of pressurized fluid to the first motor M1. However, due to the generally low pressure in the tank line TL, such as that provided by the check valve CV (where the first motor M1 should receive a replacement flow of pressurized fluid from the tank line TL), and due to pressure losses in the pressurized fluid flow, a sufficient replacement flow of pressurized fluid to prevent cavitation of the first motor M1 may not be received by the first motor M1.

[0049] To prevent cavitation from occurring in at least one of the motors M1, M2, M3, and M4 of the feed device 9, the control loop 10 is arranged to include a valve device 11 in the tank line TL (i.e., between the directional control valve DCV and the tank TK). The valve device 11 is arranged to generate sufficient pressure in the tank line TL to affect the pressurized fluid flow in the tank line TL in order to fill one or more volumes in which cavitation is likely to occur. Figure 3 The diagram illustrates an embodiment of the valve device 11 applied in control loop 10. Because the tank pressure is not always constant, the valve device 11 is configured to generate only the pressure increase required in the tank line TL to allow a replacement flow of pressurized fluid to enter the volume where cavitation is possible. This replacement flow of pressurized fluid (which can also be considered an additional flow of the required pressurized fluid) provides a filling fluid flow to the corresponding input or volume to prevent cavitation in that volume. The valve device 11 is specifically arranged to generate a pressure increase in the tank line TL to the extent that a predefined minimum pressure is achieved in the first intermediate volume V1 and / or the second intermediate volume V2. The pressures in the first intermediate volume V1 and the second intermediate volume V2 are the pressures to be controlled, and a first pressure relief member PR-AC1 and a second pressure relief member PR-AC2, having anti-cavitation valves, are used to set the predefined minimum pressure based on these controlled pressures in the first intermediate volume V1 and the second intermediate volume V2.

[0050] exist Figure 3 In this embodiment, the valve device 11 includes a back pressure valve BPV in the tank line TL. The back pressure valve BPV is arranged to generate sufficient pressure in the tank line TL to allow a replacement flow of pressurized fluid through the tank line TL to fill the cavitation-prone volumes in the control loop 10, and specifically to fill the volumes of intermediate volumes V1 and V2. Furthermore, if there is insufficient pressure in either the first intermediate volume V1 or the second intermediate volume V2, the volumes of the first connecting line CL1 and the second connecting line CL2 will also receive a replacement flow of pressurized fluid when needed. This means that the volumes of the first connecting line CL1 and the second connecting line CL2 can be better filled with pressurized fluid even though they are not monitored by the back pressure valve BPV.

[0051] Figure 3 The back pressure valve BPV of the embodiment includes a pressure control valve PCV and a spring-piloted spool thereof. The pressure control valve PCV is arranged to restrict the flow of pressurized fluid into the tank TK. The pressure control valve PCV in Figure 3The embodiment uses a 4-way 3-position valve. The pressure control valve PCV has two main operating positions: a first operating position schematically indicated by reference numeral P1 and a second operating position schematically indicated by reference numeral P2. In the first operating position, the connection from tank line TL to tank TK is fully open via the pressure control valve PCV; in the second operating position, the connection from tank line TL to tank TK is fully closed via the pressure control valve PCV. However, the pressure control valve PCV is fully operable in the operating positions between the main operating positions, thereby allowing the connection from tank line TL to tank TK to be partially opened to varying degrees.

[0052] Figure 3 The back pressure valve BPV in this embodiment also includes a pressure source PS, which is connected to the pressure control valve PCV via a pilot pressure line PPL, and specifically to the pilot control connection PCC in the pressure control valve PCV. The pressure source PS is configured to provide a pilot pressure to the pressure control valve PCV to keep the pressure control valve PCV open during normal operation of the feed device 9 (i.e., when there is no tendency for cavitation to occur in the intermediate volumes V1 and V2 in the control loop 10). The preload of the spring in the valve core of the pressure control valve PCV determines the minimum pilot pressure of the pressure control valve PCV. The pressure control valve PCV begins to close when the pressure in the pilot control connection PCC of the pressure control valve PCV is at most equal to this minimum pilot pressure. The predefined minimum pressure of the controlled pressure in the first intermediate volume V1 and the second intermediate volume V2 is set to correspond to this minimum pilot pressure of the pressure control valve PCV.

[0053] exist Figure 3 In this implementation, the pressure source PS is implemented using a pressure reducing valve PRV, which has a pressurization connection to the pump PU and a connection to the tank TK via the discharge line DR. However, other implementations of the pressure source PS are possible.

[0054] The pilot pressure line PPL also includes a throttle valve TH1 to prevent excessive pressure fluid flow through the pressure reducing valve PRV, thereby preventing the pilot pressure line PPL from becoming blocked (which would hinder the proper operation of valve assembly 11). The dominant pressure in the pilot pressure line PPL remains substantially constant, meaning it does not change frequently, but its level may vary occasionally. For valve assembly 11 to operate properly, the dominant pressure level in the pilot pressure line PPL should be higher than the pressure required to open the spool of the pressure control valve PCV, i.e., the minimum pressure, which is sufficient to overcome the force in the spring of the pressure control valve PCV.

[0055] Figure 3The valve device 11 in this embodiment further includes a first check valve CV1 and a second check valve CV2. The first check valve CV1 is connected to a first intermediate volume V1 for sensing the pressure in the first intermediate volume V1, and the second check valve CV2 is connected to a second intermediate volume V2 for sensing the pressure in the second intermediate volume V2. The first check valve CV1 and the second check valve CV2 are connected to a pilot pressure line PPL via a pressure sensing line PSL, such that the first check valve CV1 is arranged between the pilot pressure line PPL and the first intermediate volume V1, and the second check valve CV2 is arranged between the pilot pressure line PPL and the second intermediate volume V2. The first check valve CV1 is arranged in parallel with a first pressure relief member PR-AC1 having an anti-cavitation valve, such that they both sense the same dominant pressure in the first intermediate volume V1, and the second check valve CV2 is arranged in parallel with a second pressure relief member PR-AC2 having an anti-cavitation valve, such that they both sense the same dominant pressure in the second intermediate volume V2.

[0056] During normal operation of the feed device 9 at the head of the harvester 4, the control circuit 10 equipped with valve device 11 operates as described above, except that a pressure control valve PCV is present, through which pressurized fluid flow returning from motors M1, M2, M3, and M4 flows into the tank TK. Under normal operating conditions, the pressure in the first intermediate volume V1 and the second intermediate volume V2 is significantly higher than the pressure in the pilot pressure line PPL and the pressure sensing line PSL, resulting in no flow through the first check valve CV1 and the second check valve CV2 to the corresponding intermediate volumes V1 and V2. The pressure control valve PCV is fully open. The pressure control valve PCV is opened by the pressure supplied through the pilot control connection PCC to the pressure reducing valve PRV via the pilot pressure line PPL, overcoming the force in the spring of the valve core in the pressure control valve PCV. During normal operation of the feed device 9, there is an appropriate pressure available to maintain this pilot pressure. Because the pressure control valve PCV is fully open, no additional back pressure is generated in the tank line TL.

[0057] In abnormal operating conditions, where the pressure in at least one of the first intermediate volume V1 or the second intermediate volume V2 begins to drop for some reason, the operation of the control loop 10, which is used to provide sufficient pressure in the tank line TL to prevent cavitation from occurring in the intermediate volumes V1 and V2 of the control loop 10, is affected. Figure 3 The operation of the control loop 10 in the implementation method is as follows:

[0058] At least one of the first check valve CV1 or the second check valve CV2 opens in response to a pressure drop in the corresponding intermediate volumes V1, V2 falling below a predefined minimum pressure of the controlled pressure in the first intermediate volume V1 and the second intermediate volume V2. As described above, this predefined minimum pressure of the controlled pressure in the first intermediate volume V1 and the second intermediate volume V2 is set to correspond to the minimum pilot pressure of the pressure control valve PCV, and below the minimum pilot pressure level, it is assumed that a tendency for cavitation to begin to appear in the intermediate volumes V1, V2 is present. The pressure level set by the pressure reducing valve PRV in the pressure pilot line PPL can be, for example, 30 bar, which is much higher than the operating pressure in the control loop 10 and the intermediate volumes V1, V2 during normal operation of the feed device 9.

[0059] In response to the opening of at least one of the first check valve CV1 or the second check valve CV2, pressurized fluid begins to flow from the pilot pressure line PPL through the pressure sensing line PSL and the corresponding first check valve CV1 or second check valve CV2 to the corresponding intermediate volumes V1, V2. This causes a pressure drop in the pressure sensing line PSL because the orifice from the pressure reducing valve PRV restricts the flow of pressurized fluid to the pressure sensing line PSL.

[0060] In response to the pressure in the pressure sensing line PSL beginning to decrease, the pressure control valve PCV begins to close under the force of a spring in its spool. This is because the pressure in the pilot control connection PCC affecting the pressure control valve PCV begins to decrease below the minimum pilot pressure of the pressure control valve PCV due to the pressure drop in the pressure sensing line PSL. Therefore, the pressure in the pressure sensing line PSL provides the pressure controlling the degree of opening of the pressure control valve PCV under operating conditions, wherein the pressure in at least one of the first intermediate volume V1 or the second intermediate volume V2 begins to decrease below a predefined pressure level. In response to the pressure control valve PCV beginning to close, the pressure in the tank line TL begins to increase. In response to the increase in pressure in the tank line TL, the intermediate volumes V1 and V2, with their decreasing pressure, begin to fill with a replacement flow of pressurized fluid through the corresponding pressure relief components PR-AC1 and PR-AC2 equipped with anti-cavitation valves.

[0061] The pressure control valve PCV increases the pressure in the tank line TL to achieve a specific pressure level in the tank line TL as predefined by the preload of the spring in the valve core of the pressure control valve PCV. In other words, the pressure control valve PCV regulates the pressure in the tank line TL based on the spring force and the pressure in the pressure sensing line PSL. Because the pressure level set in the pressure control valve PCV is set to correspond to the minimum permissible pressure occurring in the intermediate volumes V1, V2 during normal operation of the control loop 10, the valve assembly 11 prevents the pressure in the intermediate volumes V1, V2 from falling below the set predefined pressure level.

[0062] Using the spring-guided spool in the pressure control valve PCV, a constant minimum pressure level can be set. This constant minimum pressure level is the dominant pressure level allowed in the volume that is to be monitored or sensed in the control circuit 10 before the valve device 11 is activated. If the spring is replaced by an adjustable spring, or by hydraulic or electric pilot operation, the minimum pressure level to be set can also be easily adjusted.

[0063] The valve device 11, arranged in the tank line TL, is thus configured to sense the dominant pressure in the intermediate volumes V1, V2, and to increase the dominant pressure in the tank line TL in response to a drop in pressure in the intermediate volumes V1, V2 below a level considered permissible during normal operation of the feed device 9, thereby supplying a replacement flow of pressurized fluid through the tank line TL to the intermediate volumes V1, V2. The disclosed solution is a relatively simple solution for avoiding cavitation in the control loop 10, requiring only a few additional valves without any modification to the basic construction of the control loop 10.

[0064] If there are very high requirements for the replacement flow of pressurized fluid through the pressure relief components PR-AC1 and PR-AC2 with anti-cavitation valves, then the pressure in the tank line TL can be increased to such a high level that the feed pressure regulation will be satisfied. Valve device 11 can satisfy this, but it is still undesirable to have excessively high pressure in the tank line TL. According to the embodiment for avoiding the generation of excessively high pressure in the tank line TL, i.e., limiting the highest possible dominant pressure in the tank line TL (this embodiment is also... Figure 3As shown in the diagram, valve assembly 11 includes a third check valve CV3 with a predefined opening pressure differential. The third check valve CV3 is connected between tank line TL and the pilot control connection PCC of pressure control valve PCV. The third check valve CV3 is also connected in tank line TL between directional control valve DCV and pressure control valve PCV. The third check valve CV3 provides pressure relief in tank line TL by limiting the highest possible pressure in tank line TL. When the pressure in tank line TL rises above the opening pressure of the third check valve CV3, the third check valve CV3 opens, allowing pressurized fluid to flow from tank line TL to the pilot control connection PCC of pressure control valve PCV. This increases the pressure in the pilot control connection PCC of pressure control valve PCV, thereby forcing pressure control valve PCV to open or open further to allow pressurized fluid or more pressurized fluid to flow from tank line TL through pressure control valve PCV into tank TK, thus limiting the dominant highest possible pressure in tank line TL.

[0065] Figure 3 The implementation also includes a throttle valve TH2 between the third check valve CV3 and the pressure sensing line PSL. The throttle valve TH2 has the function of restricting the flow from the pilot control connection PCC of the pressure control valve PCV to the pressure sensing line PSL, and thus enables the pressure on the pilot control connection PCC of the pressure control valve PCV to be increased above the dominant pressure in the pressure sensing line PSL, so as to limit the maximum pressure in the tank line TL.

[0066] Figure 4 A second embodiment of the control circuit 10, including a valve device 11 for controlling the operation of the harvester head 4 of the harvester 1, is schematically shown. Figure 4 The control loop is basically similar to Figure 3 The control loop differs in that the third motor 3 and the fourth motor 4 are multi-speed motors that allow the use of multiple speeds when feeding the tree 8 forward and backward in the head of the harvester 4. The basic structure and operation of the various applicable multi-speed motors are well known to those skilled in the art and therefore will not be considered in more detail herein.

[0067] Due to the multi-speed motor structure, additional motor volumes exist in the third motor M3 and the fourth motor M4. Therefore, in addition to the connections of the third motor M3 and the fourth motor M4 to the corresponding intermediate volumes V1 and V2, they are also directly connected to the first connecting line CL1, i.e., to port A in the directional control valve DCV. Because... Figure 4With this structure of the control loop 10, during the operation of the forward feed tree 8, it is also possible that, due to the direct connection to port A in the directional control valve DCV and / or due to insufficient flow rate of the pressurized fluid from the first motor M1 and / or the second motor M2 to the corresponding third motor M3 and / or the fourth motor M4, at least one of the third motors M3 or the fourth motor M4 may rotate faster relative to the other motor, thereby causing possible cavitation in the third motor M3 or the fourth motor M4.

[0068] With Figure 3 In a similar manner to that disclosed in the embodiments, valve device 11 can sense or detect pressure losses that may occur in the third motor M3 or the fourth motor M4 when feeding the tree 8 forward, and pressure losses that may occur in the first motor M1 or the second motor M2 when feeding the tree 8 backward, and generate sufficient pressure in the tank line TL to prevent cavitation from occurring in any of these motors. Figure 4 In this process, valve device 11 operates in the same manner in both directions, so it is independent of the feed direction of tree 8 through harvester head 4.

[0069] Figure 5 A third embodiment of a control circuit 10 is schematically shown, including a valve device 11 for controlling the operation of the harvester head 4 of the harvester 1. Figure 5 The control loop is basically similar to Figure 3 The control loop, but the difference lies in the control loop. Figure 5 In this implementation, it is assumed that the cavitation phenomenon described above may occur only in relation to one of the intermediate volumes V1 and V2, and more specifically, in relation to the first intermediate volume V1. The basic operation of the control loop 10 is as described above, but considering... Figure 3 The implementation method can reduce the valve device 11.

[0070] exist Figure 5 In one embodiment, the valve device 11 also includes a back pressure valve BPV in the tank line TL, the back pressure valve BPV being arranged to generate sufficient pressure in the tank line TL to fill the first intermediate volume V1 in the control loop 10 to prevent possible cavitation on one side of the first intermediate volume V1.

[0071] exist Figure 5 In the implementation of this method, the back pressure valve BPV only includes the pressure control valve PCV, the structure and operation of which have been discussed in more detail above.

[0072] Valve assembly 11 also includes a pressure sensing line PSL, through which the pressure control valve PCV is directly connected to the first intermediate volume V1. Therefore, the pressure sensing line PSL effectively also functions as the pressure pilot line PPL, and the preload of the spring in the spool of the pressure control valve PCV is set to correspond to the lowest pressure occurring in the first intermediate volume V1 during normal operation of the control loop 10. In other words, the preload of the spring in the spool of the pressure control valve PCV determines a predefined pressure level; below this predefined pressure level, it is assumed that a tendency for cavitation to begin to occur in the intermediate volume V1.

[0073] In an abnormal operating condition, where the pressure in the first intermediate volume V1 begins to drop below the minimum pressure present in the intermediate volume V1 during normal operation of control loop 10 for some reason, the pressure in the pressure sensing line PSL begins to drop, and the pressure control valve PCV begins to close as if by the spring force of the valve core within the pressure control valve PCV. Therefore, the pressure in the pressure sensing line PSL also provides pressure to the pressure control valve PCV to control the degree of opening of the pressure control valve PCV. In response to the pressure control valve PCV beginning to close, the pressure in the tank line TL begins to increase, and in response to the increase in pressure in the tank line TL, the intermediate volume V1 with its decreasing pressure begins to be filled with a replacement flow of pressurized fluid through the first pressure relief element PR-AC1 with an anti-cavitation valve. The pressure control valve PCV increases the pressure in the tank line TL until a predefined pressure corresponding to the minimum pressure present in the first intermediate volume V1 during normal operation of control loop 10 is again present in the pressure sensing line PSL, thereby returning the operating position of the pressure control valve PCV to a position where the pressure control valve PCV is substantially fully open.

[0074] exist Figure 5 In this implementation, only the pressure control valve PCV is present, but the check valve CV1 or the pressure source PS is not required, because the controlled pressure (i.e., the pressure that dominates in the first intermediate volume V1) can be directly operated as the pressure for controlling the pressure control valve PCV.

[0075] With and according to Figure 3 The same manner as disclosed in the embodiments disclosed herein. Figure 5An implementation may include a check valve CV3 connected between tank line TL and the pilot control connection PCC of pressure control valve PCV to limit the highest possible pressure in tank line TL. When the pressure in tank line TL rises above the opening pressure of check valve CV3, check valve CV3 opens, allowing pressurized fluid to flow from tank line TL to the pilot control connection PCC of pressure control valve PCV. This, in turn, increases the pressure in the pilot control connection PCC of pressure control valve PCV, thereby forcing pressure control valve PCV to open or open further to allow pressurized fluid or more pressurized fluid to flow from tank line TL through pressure control valve PCV into tank TK, thus limiting the highest possible pressure in tank line TL.

[0076] Figure 5 The implementation also includes a throttle valve TH2 between the check valve CV3 and the pressure sensing line PSL. The throttle valve TH2 here again serves to restrict the flow from the directional control valve DCV pilot to the pressure sensing line PSL, thereby enabling the pressure on the pilot control connection PCC of the pressure control valve PCV to be increased above the dominant pressure in the pressure sensing line PSL, in order to limit the maximum pressure in the tank line TL.

[0077] Figure 6 Exemplary measurements illustrating the operation of the anti-cavitation valve device 11 according to an embodiment are disclosed. Figure 6 The upper curve in the figure shows the measured pump pressure P. pump The pressure fluid flow rate Q at the head of the harvester 4 hhead The pressure p in the intermediate volumes V1 and V2 V1 p V2 And the pressure p in ports A and B of the directional control valve DCV A -Forward, p B -Backwards. In Figure 6 The lower graph shows the measured pressure on the pressure sensing line (“Sensing Line” in the graph), the box pressure in the box of the harvester head 4 without a back pressure valve BPV (“T Base Machine” in the graph), and the box pressure in the box of the harvester head 4 with a back pressure valve BPV (“T Harvester Head” in the graph), as well as the feed rate of the tree 8 in the harvester head 4 (“Feed Rate” in the graph). In this measurement example, the tree 8 is difficult to feed; it is bent and has large branches.

[0078] Initially, the directional control valve DCV opens to the directional PABT, thus activating the forward feed. Initially, the tree accelerates and begins feeding normally. From the start, the fourth feed member FM4 begins to release its clamp and slide, and the tree stops. This results in an operating condition at point 0.4s, where the fourth motor M4 slides and the second motor M2 cannot supply sufficient pressurized fluid flow to the second intermediate volume V2 of the fourth motor M4, causing a pressure drop in the second intermediate volume V2, thus creating a risk of cavitation in the input of the fourth motor M4 on one side of the second intermediate volume V2. Simultaneously, the pressure in the pressure sensing line PSL follows the pressure in the second intermediate volume V2. When the pressure drops below 20…25 bar, the anti-cavitation valve device begins to close, and thus a higher pressure is generated in the box line TL at the harvester head. This higher pressure ensures that the second pressure relief member PR-AC2 with an anti-cavitation valve on one side of the second intermediate volume V2 meets the need for a replacement flow of pressurized fluid to the fourth motor M4, and the fourth motor M4 does not begin to cavitate. As long as the directional control valve DCV moves forward to feed the tree, the sliding will continue.

[0079] At 0.8s, the harvester head 4 begins to feed the tree backward. Immediately after the start of backward feeding, the pressure on one side of the first intermediate volume V1 begins to drop rapidly. This means that the feed components associated with the upper feed motor (i.e., the first motor M1 and the second motor M2) and the lower feed motor (i.e., the fourth motor M4) on one side of the second intermediate space are sliding. This means that if the pressure is too low, the first motor M1 will move towards cavitation. Furthermore, in this situation, because the pressure in the pressure sensing line PSL is too low, the valve device 11 generates an increase in the pressure in the tank line TL to fill the control loop 10 on one side of the first intermediate volume V1 and thus prevent cavitation.

[0080] It will be apparent to those skilled in the art that, with advancements in technology, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above, but can be varied within the scope of the claims.

Claims

1. A control circuit (10) for a feed device (9) in a harvester head (4), the control circuit (10) comprising: A set of motors (M1, M2, M3, M4) arranged to operate a set of feed components (FM1, FM2, FM3, FM4) in the head of the harvester (4) to feed a tree (8) through the head of the harvester (4). The set of motors (M1, M2, M3, M4) includes: a first motor (M1) and a second motor (M2) connected in parallel; a third motor (M3); and a fourth motor (M4), the third motor (M3) connected in series with the first motor (M1) such that a first intermediate volume (V1) exists between the first motor (M1) and the third motor (M3), and the fourth motor (M4) connected in series with the second motor (M2) such that a second intermediate volume (V2) exists between the second motor (M2) and the fourth motor (M4). A pressure line system (PL, CL1, CL2) and a tank line (TL) are provided, the pressure line system (PL, CL1, CL2) being arranged to deliver pressurized fluid to the set of motors (M1, M2, M3, M4) to operate the set of motors (M1, M2, M3, M4), and the tank line (TL) being used to receive the return flow of the pressurized fluid from the set of motors (M1, M2, M3, M4). Its features are: The control loop (10) includes: A pressure sensing line (PSL) is provided for sensing pressure in at least one input of at least one of the group of motors (M1, M2, M3, M4) or in at least one intermediate volume (V1, V2) of the first intermediate volume and the second intermediate volume, to detect a decrease in pressure in the at least one input of the at least one motor (M1, M2, M3, M4) or in the at least one intermediate volume (V1, V2), and A pressure control valve (PCV), disposed at the tank line (TL) and connected to the pressure sensing line (PSL), is configured to, in response to a sensed pressure drop in at least one input of the at least one motor (M1, M2, M3, M4) or in the at least one intermediate volume (V1, V2), generate an increase in pressure in the tank line (TL) such that a replacement flow of the pressurized fluid passes through the tank line (TL) to the at least one input of the at least one motor (M1, M2, M3, M4) or to the at least one intermediate volume (V1, V2). A pressure source (PS) is connected to the pressure control valve (PCV) via a pilot pressure line (PPL) arranged to provide pilot pressure to the PCV. The pressure sensing line (PSL) is connected between the pilot control connection (PCC) of the pressure control valve (PCV) and the pressure source (PS) for controlling the opening degree of the pressure control valve (PCV). The pressure in the pressure sensing line (PSL) is arranged to decrease in response to a sensed pressure drop in at least one input of the at least one motor (M1, M2, M3, M4) or in the at least one intermediate volume (V1, V2), and the opening degree of the pressure control valve (PCV) is arranged to decrease to produce an increase in pressure in the tank line (TL), such that a replacement flow of the pressurized fluid reaches at least one input of the at least one motor (M1, M2, M3, M4) or reaches the at least one intermediate volume (V1, V2).

2. The control loop according to claim 1, characterized in that, The pressure sensing line (PSL) includes a first check valve (CV1) and a second check valve (CV2), the first check valve (CV1) for sensing the dominant pressure in the first intermediate volume (V1), and the second check valve (CV2) for sensing the dominant pressure in the second intermediate volume (V2). In response to a decrease in the sensed pressure, the corresponding check valves (CV1, CV2) are arranged to open, so that the pressure in the pressure sensing line (PSL) decreases in response to the pressure fluid flow through the corresponding check valves (CV1, CV2) to the corresponding intermediate volumes (V1, V2).

3. The control loop according to claim 1 or 2, characterized in that, The control loop (10) also includes a check valve (CV3) connected to the tank line (TL) to limit the pressure supplied by the back pressure valve (BPV) in the tank line (TL).

4. The control loop according to claim 1 or 2, characterized in that, The control loop (10) includes pressure relief components (PR-AC1, PR-AC2) with anti-cavitation valves corresponding to each intermediate volume (V1, V2) in the tank line (TL), and the replacement flow of the pressure fluid is arranged to flow into the at least one intermediate volume (V1, V2) through the corresponding pressure relief components (PR-AC1, PR-AC2) with anti-cavitation valves in response to a sensed pressure drop in the at least one intermediate volume (V1, V2).

5. The control loop according to claim 1 or 2, characterized in that, A valve device (11) is arranged at the tank line (TL) to sense a pressure drop in one of the at least one input of the at least one motor (M1, M2, M3, M4) or one of the at least one intermediate volume (V1, V2) below a predefined pressure level, and in response to the sensed pressure drop in one of the at least one input of the at least one motor (M1, M2, M3, M4) or one of the at least one intermediate volume (V1, V2) below the predefined pressure level, to generate an increase in pressure in the tank line (TL) so that a replacement flow of the pressure fluid enters through the tank line (TL) into one of the at least one input of the at least one motor (M1, M2, M3, M4) or one of the at least one intermediate volume (V1, V2).

6. A method for controlling a control loop (10) of a feed device (9) in a harvester head (4), wherein, The control loop (10) includes: A set of motors (M1, M2, M3, M4) arranged to operate a set of feed components (FM1, FM2, FM3, FM4) in the head of the harvester (4) to feed a tree (8) through the head of the harvester (4). The set of motors (M1, M2, M3, M4) includes: a first motor (M1) and a second motor (M2) connected in parallel; a third motor (M3); and a fourth motor (M4), the third motor (M3) connected in series with the first motor (M1) such that a first intermediate volume (V1) exists between the first motor (M1) and the third motor (M3), and the fourth motor (M4) connected in series with the second motor (M2) such that a second intermediate volume (V2) exists between the second motor (M2) and the fourth motor (M4). A pressure pipeline system (PL, CL1, CL2) and a tank line (TL) are provided, the pressure pipeline system (PL, CL1, CL2) being arranged to deliver pressurized fluid to the set of motors (M1, M2, M3, M4) to operate the set of motors (M1, M2, M3, M4), and the tank line (TL) being used to receive the return flow of the pressurized fluid from the set of motors (M1, M2, M3, M4). Its features are: The control loop (10) also includes: A pressure sensing line (PSL) is used to sense the pressure in at least one input of at least one of the group of motors (M1, M2, M3, M4) or in at least one intermediate volume (V1, V2) of the first intermediate volume and the second intermediate volume. A pressure control valve (PCV) is disposed at the tank line (TL) and connected to the pressure sensing line (PSL) via a pilot control connection (PCC) of the pressure control valve (PCV). A pressure source (PS) is connected to the pressure control valve (PCV) via a pilot pressure line (PPL) arranged to provide pilot pressure to the PCV, and a pressure sensing line (PSL) is connected between the pilot control connection (PCC) of the PCV and the pressure source (PS) for controlling the opening degree of the pressure control valve (PCV). Pressure in at least one input of the at least one motor (M1, M2, M3, M4) or in at least one intermediate volume (V1, V2) is sensed to detect a decrease in pressure in at least one input of the at least one motor (M1, M2, M3, M4) or in at least one intermediate volume (V1, V2), and In response to a sensed pressure drop in at least one input of the at least one motor (M1, M2, M3, M4) or in the at least one intermediate volume (V1, V2), the pressure in the tank line (TL) is increased by reducing the opening of the pressure control valve (PCV) so that a replacement flow of the pressure fluid enters through the tank line (TL) into the at least one input of the at least one motor (M1, M2, M3, M4) or into the at least one intermediate volume (V1, V2).

7. The method according to claim 6, wherein, The pressure sensing line (PSL) includes a first check valve (CV1) and a second check valve (CV2), the first check valve (CV1) for sensing the dominant pressure in the first intermediate volume (V1), and the second check valve (CV2) for sensing the dominant pressure in the second intermediate volume (V2). In response to a decrease in the sensed pressure, the corresponding check valves (CV1, CV2) open, so that the pressure in the pressure sensing line (PSL) decreases in response to the pressure fluid flow through the corresponding check valves (CV1, CV2) to the corresponding intermediate volumes (V1, V2).

8. The method according to claim 6 or 7, wherein, The control loop (10) includes a check valve (CV3) connected to the tank line (TL) to limit the pressure supplied by the back pressure valve (BPV) in the tank line (TL).

9. The method according to claim 6 or 7, wherein, The control loop (10) includes pressure relief components (PR-AC1, PR-AC2) with anti-cavitation valves corresponding to each intermediate volume (V1, V2) in the tank line (TL), whereby the replacement flow of the pressure fluid flows into the at least one intermediate volume (V1, V2) through the corresponding pressure relief component (PR-AC1, PR-AC2) in response to a sensed pressure drop in the at least one intermediate volume (V1, V2).

10. The method according to claim 6 or 7, characterized in that, Sensing that the pressure in one of the at least one input of the at least one motor (M1, M2, M3, M4) or one of the at least one intermediate volume (V1, V2) drops below a predefined pressure level, and in response to the sensed pressure drop in one of the at least one input of the at least one motor (M1, M2, M3, M4) or one of the at least one intermediate volume (V1, V2) dropping below the predefined pressure level, increasing the pressure in the tank line (TL) to allow a replacement flow of the pressure fluid to enter one of the at least one input of the at least one motor (M1, M2, M3, M4) or one of the at least one intermediate volume (V1, V2) through the tank line (TL).

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