Hydraulic control system and method for shovel swing operation in a work machine having a hydraulic pump and an unloading valve

Abstract

An excavator or other working machine includes a tiltable bucket operable by a hydraulic actuator, controlled by a bucket control valve responsive to control signals including a bucket swing control signal which causes the bucket to be repeatedly moved in a swing operation in a frame and dump direction to swing debris from the bucket. The actuator is powered by pressure from a hydraulic pump, and the control system includes an unloading valve to release pressure from a supply line to unload the pump when power is not required. The control system is arranged to maintain a constant pressure signal in a load sense line to constantly maintain the unloading valve in a closed state for the duration of the bucket swing operation. This can be achieved by pressurising the actuator of a quick hitch to lock the bucket to the machine.

Description

Technical Field

[0001] This invention relates to a hydraulic power system in working machinery (e.g., an excavator) having a bucket tiltable between a frame (upward) position and a tilting (downward) position, wherein the machinery includes a hydraulic pump and an unloading valve. Background Technology

[0002] Such systems typically include a load sensing (LS) network to control pump operation, thereby reducing input energy when the various hydraulic actuators and motors in the machine require little power, and increasing power when the pressure in the pump's supply line must be maintained at a higher flow rate to drive one or more of the actuators or motors in use. The LS network transmits a pressure signal (referred to herein as LS pressure) in response to pressure demand, which controls the pump's operation.

[0003] The pressure signal can be obtained simply by connecting the hydraulic lines of the LS network to the hydraulic lines that supply pressure from their respective control valves to each actuator or motor; thus, when the valve is opened, the supply pressure is applied to the actuator or motor and simultaneously to the LS network.

[0004] Hydraulic pressure can be supplied from a variable displacement pump, such as a piston pump, where the displacement is controlled by the position of a rotating swashplate via LS pressure control. In this case, a low LS pressure will reduce the pump displacement, allowing the pump to continue rotating without increasing the pressure in the main supply line.

[0005] However, variable displacement pumps are complex and expensive, and simpler fixed displacement pumps, such as gear pumps, are generally preferred. In such systems, to provide a simple transmission that drives the pump at a constant speed corresponding to the prime mover speed, an unloading valve is required in the main supply line from the pump. When the actuator demands pressure, the LS pressure increases. The high LS pressure closes the unloading valve, which allows pressure to build up in the main supply line to the normal operating pressure, making it more difficult for the pump (and therefore the prime mover) to operate to maintain the flow to the actuator at the normal operating pressure. When demand stops, the LS pressure decreases and allows the unloading valve to open at a lower idling pressure (which can be set, for example, by a 10-bar bias spring) to release pressure in the main supply line, allowing the fixed displacement pump to continue rotating with the prime mover under minimal load.

[0006] In machinery with tilting buckets, mud and other debris often adhere to the bucket during use. The operator will move the bucket rapidly along the frame and in the tilting direction, causing the bucket to shake violently to dislodge the debris.

[0007] In smaller machines, this can be achieved by rapidly and repeatedly moving the joystick (which controls the movement of the bucket) between the frame and the dump command position. In more complex machines, to make this operation easier for the operator, a separate bucket rocking control can be provided, which moves the bucket in this pattern when actuated by the operator.

[0008] User input (whether it is a series of alternating joystick signals or a dedicated bucket rocking control output signal) will cause the movement of a valve (e.g., a valve spool), which will apply hydraulic pressure from the supply line to one or more bucket actuators to perform this rapid, alternating frame-dump-frame-dump movement of the bucket.

[0009] For example, in a common arrangement, the joystick sends an electrical signal to a solenoid actuator, which in turn operates a pilot valve. The pilot valve sends pilot pressure to the hydraulic actuator of the main bucket control spool valve, which in turn sends the main supply pressure to the bucket actuator. The main supply pressure applied to the bucket actuator is also applied via the LS network to close the unloading valve, making it more difficult for the pump (and therefore the prime mover) to respond to the power demands of moving the bucket and maintain normal operating pressure.

[0010] In practice, it has been found that this arrangement may sometimes be less than satisfactory, as discussed further below under the heading: "Industrial Practicality". Summary of the Invention

[0011] In a first aspect, the present invention provides a control system for machinery.

[0012] The machine includes: a hydraulic pump for supplying hydraulic pressure to a supply line; a bucket; at least one bucket actuator hydraulically operable to tilt the bucket between an upward-facing frame position and a downward-facing dumping position; and at least one user controller user operable to generate control signals, including bucket rocking control signals.

[0013] The control system includes an unloading valve with an unloading valve actuator. The unloading valve can be opened in use to release hydraulic pressure from the supply line to unload the hydraulic pump, and can be closed by the unloading valve actuator.

[0014] The control system further includes: a load sensing circuit, which is arranged to apply a pressure signal to an unloading valve actuator in response to a demand for hydraulic power to close the unloading valve and thereby maintain hydraulic pressure in the supply line;

[0015] The control system further includes: a bucket control valve, operable in use by a control signal to apply hydraulic pressure from a supply line to at least one bucket actuator; the bucket control valve is operable in use to cause at least one bucket actuator to perform a bucket swaying operation in response to a bucket swaying control signal, the bucket swaying operation being a repetitive movement of the bucket alternately toward a frame position and a dump position to sway debris from the bucket.

[0016] The control system is configured to maintain a constant pressure signal in the load sensing circuit so as to keep the unloader valve constantly closed during the duration of the bucket rocking operation.

[0017] In a related respect, the present invention provides a machine having the control system described above.

[0018] On the other hand, the present invention provides a method for controlling such a machine.

[0019] The method includes operating a bucket control valve in response to a bucket rocking control signal to cause at least one bucket actuator to perform a bucket rocking operation; and maintaining a constant pressure signal in a load sensing circuit to keep the unloader valve constantly closed during the duration of the bucket rocking operation. Attached Figure Description

[0020] Further features and advantages will become apparent from the illustrative embodiments described hereof, by way of example only and not by way of limiting the scope of the claims, and with reference to the accompanying drawings, wherein:

[0021] Figure 1 Key components of a machine including a control system according to one embodiment are shown;

[0022] Figure 2 The machine is shown;

[0023] Figure 3 The bucket of the machine is shown in frame position;

[0024] Figure 4 The bucket is shown in the dumping position;

[0025] Figure 5 The bucket, detached from the mounting hardware, is shown.

[0026] Figure 6 A bucket connected to a mounting is shown, with the coupling mechanism in the released position;

[0027] Figure 7 A bucket connected to the mounting bracket is shown, with the coupling mechanism in the locked position; and

[0028] Figure 8 This is a flowchart illustrating an embodiment of the method.

[0029] Reference numbers and characters appearing in more than one figure indicate the same or corresponding elements in each of them. Detailed Implementation

[0030] Reference Figure 2 The machine 1 includes a bucket 2 and at least one bucket actuator 3, the bucket actuator being hydraulically operable to position the bucket 2 in an upward-facing frame position along opposite frame and dumping directions. Figure 3 ) and downward dumping position ( Figure 4 The two sides are inclined.

[0031] Machinery 1 can be configured as a steerable land vehicle mounted on wheels or tracks 4, and can be, for example, an excavator (as shown) or a backhoe loader. For example, the total weight of the machinery can exceed 1.5 tons, or 5 tons, or 10 tons, or 20 tons, up to 100 tons or more.

[0032] Also refer to Figure 5-7 The bucket 2 can be mounted on the machinery via a quick-connect coupling 5, known in the art, which includes a mounting member 6 and a coupling mechanism 7 operated by at least one second actuator 8 to selectively lock the bucket to the mounting member. The mounting member 6 may be located at the distal end of a first arm or rod 9, which in turn is mounted at the distal end of a second arm or boom 10, wherein both arms 9, 10 are movable in rotation by a hydraulic actuator 11. In the example shown, the bucket actuator 3 is a hydraulic cylinder mounted on the rod 9 to rotate the mounting member 6. The bucket can be used to excavate or move loose material near the machinery and is interchangeable with other tools, such as another bucket, a hydraulic breaker, or a grab bucket.

[0033] Reference Figure 2 The machine also includes at least one user controller, as shown, which may include a joystick 12. The at least one user controller, such as the joystick 12, is operable by a user to generate control signals 13. The control signals include a bucket sway control signal 13'.

[0034] The joystick 12 can be moved in opposite directions, as indicated by the arrows, to generate bucket frame and dump control signals, i.e., signals commanding the bucket to move to the frame and dump positions, respectively. Rapid and repetitive movements of the joystick 12 between its relative positions on the axis of motion will thus generate bucket yaw control signals 13', as a series of alternating, repetitive frame and dump signals. Alternatively or additionally, user control may include dedicated bucket yaw control (not shown), such as a button, which generates the bucket yaw control signals 13' when activated by the user, without requiring rapid and repetitive user input.

[0035] The machine also includes a hydraulic pump 14 for supplying hydraulic pressure to a supply line 15. In this specification, a "line" refers to a fluid path that delivers hydraulic pressure, or multiple such fluid paths interconnected to deliver hydraulic pressure between multiple points, commonly referred to as a "network".

[0036] The hydraulic pump 14 can be a fixed displacement pump, such as a gear pump. The pump 14 can be driven to rotate by an internal combustion engine 16 or other prime mover. The fixed displacement pump 14 can be coupled to the prime mover 16 at a fixed ratio, that is, it can be driven by the prime mover at a fixed speed relative to the speed of the prime mover.

[0037] The machine further includes a control system 20, which includes an unloading valve 21, a load sensing line 25, and a bucket control valve 26.

[0038] The unloading valve 21 can be opened, for example, by hydraulic pressure generated in the supply line 15 by the pump 14, to release the hydraulic pressure from the supply line 15 and thus unload the hydraulic pump 14, and can be closed by the unloading valve closing actuator 22. The biasing spring 23 can act in the same (closing) direction as the closing actuator 22, opposite to the opening actuator 24 actuated by the pressure in the supply line 15, such that when the closing actuator 22 is not actuated, when the pressure exceeds the biasing force of the spring 23, the unloading valve 21 opens to release pressure from the supply line 15, which can be, for example, about 10 bar.

[0039] The load sensing lines 25 can form a network arranged to transmit hydraulic pressure from multiple points in the system, representing the demand for hydraulic power from any component of the machinery, such as from the hydraulic motor driving the track 4 or from any of the hydraulic actuators 3, 8, and 11. In this specification, the hydraulic pressure in the load sensing lines is also referred to as a “pressure signal” or “LS signal,” and for convenience, the load sensing lines 25 are referred to as “LS lines” or “LS network.”

[0040] LS line 25 is configured to apply a pressure signal to unloading valve closing actuator 22 in response to the demand for hydraulic power, thereby closing unloading valve 21 and maintaining hydraulic pressure in supply line 15.

[0041] The bucket control valve 26 may be a directional control spool valve, as shown, and in use may be operated directly or indirectly by control signals 13, 13' to apply hydraulic pressure from supply line 15 to at least one bucket actuator 3. Specifically, the bucket control valve 26 is operable in response to the bucket rocking control signal 13' to cause at least one bucket actuator 3 to perform a bucket rocking operation, which is a repetitive movement of the bucket 2 alternately between the frame and dump positions, that is, alternating repetitive movement in the frame and dumping directions toward the frame and dump positions, to rock debris from the bucket. During the bucket rocking operation, the bucket may move from the frame position to the dump position and back again, or may move between the frame and dump positions through a more limited range of movement. The bucket or bucket actuator may engage a stop in one or both of the frame and dump positions to generate an impact that helps to separate debris from the bucket, or the rocking action may be achieved without impacting the stop. For example, the bucket can repeatedly move short distances from the dumping position to the support position and then return to the dumping position.

[0042] Control signals 13, 13' can be electrical signals, and the control system may include an electronic controller 17 that receives and responds to the electrical signals to control the operation of a pilot valve (not shown). The pilot valve applies hydraulic pilot pressure to a hydraulic actuator, which operates the spool of bucket control valve 26 and other control valves, which in turn supply hydraulic pressure to actuators, such as hydraulic cylinders 3, 11 that move mechanical components. Alternatively or additionally, electrical signals 13, 13' can be applied directly to the solenoid of the pilot valve or other actuators. Alternatively or additionally, electrical signals 13, 13' or electrical signals from the electronic controller 17 can be applied directly to solenoids or other electric actuators that control the movement of the spools of these valves. These actuators deliver pressure to actuators that move these mechanical components, such as the second actuator 8, which may be controlled by the solenoid shown, although it may alternatively be controlled by pilot pressure.

[0043] Those skilled in the art will be familiar with this alternative control device and will understand that Figure 2 The control system shown can be implemented in a variety of different ways. Therefore, for clarity, Figure 2 The control system depicted is simplified, and electrical signal paths, pilot valves, pilot pressure supply lines, and various other conventional details not essential for understanding the invention are not shown. Similarly, it will be understood that the valve opening and closing actuators and other functional elements are conventional and can be implemented through appropriate configurations of the valve core and housing or other sub-components known in the art, and therefore are not all shown in detail.

[0044] The control system 20 is configured to maintain a constant pressure signal in the load sensing circuit 25 during bucket rocking operation (i.e., until the bucket rocking operation stops) to keep the unloading valve 21 constantly closed. A constant pressure signal is a signal that has a constant effect within the range of keeping the unloading valve closed; that is, the signal does not fluctuate, or fluctuates in a manner or to a degree that does not cause the unloading valve 21 to open.

[0045] The control system 20 can be configured to maintain a constant pressure signal while the bucket rocking control signal 13' is continuous, and to interrupt the constant pressure signal when the bucket rocking control signal 13' stops.

[0046] Alternatively, for example, if the bucket rocking control signal 13' is generated by a dedicated bucket rocking control that requires only a single operation by the user, the control system 20 can maintain a constant pressure signal for a predetermined period of time (e.g., in response to a timer), which is triggered by receiving the bucket rocking control signal 13', and also defines the duration of the bucket rocking operation. For example, the electronic controller 17 may include a program stored in non-transient memory that, when executed on the processor of the electronic controller, commands the bucket control valve 26 to perform the bucket rocking operation in response to the bucket rocking control signal 13', and also controls the operation of one or more hydraulic valves of the control system 20 to maintain a constant pressure signal for the duration of the bucket rocking operation.

[0047] As described above, the bucket rocking control signal 13' can consist of a series of alternating control signals generated by the user through at least one user-controlled repetitive operation, such as rapidly and repeatedly moving the joystick 12 between its relative extreme positions on the motion axis controlling the tilting function of the bucket 2. In this case, the control system 20 can be configured to maintain a constant pressure signal in the load sensing circuit in response to the repetition of such alternating control signals at a frequency above a threshold frequency. For example, the threshold frequency can be defined by a certain number of transitions of the joystick 12 between the frame and the dumping position within a defined time period; for example, three transitions within a 500ms time period. Additionally, the control system 20 can be arranged to maintain a constant pressure signal while the bucket rocking control signal 13' continues to meet a defined criterion during the rolling time period, and to stop the constant pressure signal when the criterion is no longer met (i.e., when the bucket rocking control signal 13' stops—for example, when the number of transitions drops below three within the immediately preceding 500ms time period).

[0048] When the bucket sway control signal 13' consists of a series of alternating electrical control signals, the electronic controller 17 can be configured to monitor the electrical signals and determine whether the electrical signals repeat at a frequency higher than a threshold frequency.

[0049] Figure 8 An example control sequence for implementing the method of the present invention is shown.

[0050] The sequence begins in step S1 with the bucket rocking control signal 13'.

[0051] In step S2, the method continues to operate the bucket control valve 26 (e.g., electrically and / or hydraulically via pilot pressure) in response to the bucket rocking control signal 13', so that at least one bucket actuator 3 performs the bucket rocking operation.

[0052] The method includes, in step S4, maintaining a constant pressure signal in the load sensing line 25 to keep the unloading valve 21 constantly closed during the duration of the bucket rocking operation. Step S4 may be performed before, after, or simultaneously with step S2.

[0053] As described above, when the bucket sway control signal 13' consists of a series of alternating control signals, the method may include, in step S3, determining (e.g., via electronic controller 17 if they are electrical signals) whether the alternating control signals are repeated at a frequency higher than a threshold frequency. If yes (Y), the method proceeds to step S4. If no (N), the sequence returns to S3, for example, by continuing to monitor the control signals 13 via electronic controller 17 to determine whether they are individual frame or dumping signals, or whether they are repeated fast enough to constitute the bucket sway control signal 13'.

[0054] The control system 20 can be arranged to maintain a constant pressure signal in the LS line in any convenient manner. One way to achieve this is by controlling the operation of the second actuator in response to the bucket rocking control signal 13', as will now be described.

[0055] The mechanism 1 may further include at least one second actuator that is hydraulically operable. In the example shown, at least one second actuator 8 is arranged in the mounting 6 to operate the coupling mechanism 7; however, alternatively, it may be any hydraulic actuator of the mechanism that can be constantly pressurized to its limit position during bucket rocking operation.

[0056] The control system 20 includes a second actuator control valve 27 operable to apply hydraulic pressure from supply line 15 to at least one second actuator 8. The LS line is arranged to apply the hydraulic pressure from the supply line as a pressure signal to an unloading valve to close actuator 22 when applied to at least one second actuator 8. As shown, this can be achieved by obtaining the LS pressure signal from a shuttle valve 28 arranged in communication with the line supplying pressure from the second actuator control valve 27 to the second actuator 8.

[0057] The control system 20 can be configured to operate the second actuator control valve 27 (e.g., via a signal from the electronic controller 17 in response to recognizing the bucket rocking control signal 13') to constantly apply hydraulic pressure from the supply line 15 to at least one second actuator 8 during bucket rocking operation, and to apply as a pressure signal to the unloading valve closing actuator 22 via the load sensing line 25.

[0058] Now refer to Figure 5 , 6 And 7, when the bucket 2 is detachably connected to the mounting part 6 of the quick coupler (e.g. Figure 6 and 7 As shown), at least one second actuator 8 is operable to be in the locked position ( Figure 7 ) and release position ( Figure 6 The coupling mechanism 7 can be selectively moved between the two parts. In the locked position, the bucket 2 is locked to the mounting member 6 via the coupling mechanism 7. In the released position, the bucket 2 is unlocked from the mounting member 6, allowing it to be removed from the mounting member. Figure 5 As shown. In the illustrated example, the second actuator 8 is a hydraulic cylinder arranged in the mounting 6, and the coupling mechanism 7 includes a wedge 29, which is pushed by the second actuator 8 to engage in a recess 30 in the bucket 2 in a locked position. Other arrangements are also possible, as is known in the art.

[0059] The control system is arranged to operate the second actuator control valve 27 to apply hydraulic pressure from the supply line 15 to at least one second actuator 8, thereby constantly pushing the coupling mechanism 7 to a locked position during bucket rocking operation. Consequently, the piston of the hydraulic cylinder is pushed to its limit position, where the wedge 29 engages in the recess 30 and remains in this limit position during bucket rocking operation.

[0060] Therefore, it should be understood that the novel method may further include: operating the second actuator control valve 27 to constantly apply hydraulic pressure from the supply line 15 to at least one second actuator 8 during the duration of the bucket rocking operation, and applying the hydraulic pressure as an LS pressure signal to the unloading valve closing actuator 22 via the load sensing line 25. The method may further include operating the second actuator control valve 27 to apply hydraulic pressure from the supply line 15 to at least one second actuator 8, thereby constantly pushing the coupling mechanism 7 to the locking position during the bucket rocking operation.

[0061] Another shuttle valve 31 can be arranged in connection with the line supplying pressure from the bucket control valve 26 to the bucket actuator 3, which supplies an LS signal to the LS line 25 when the bucket is commanded to or toward the frame or dump position. This LS signal ensures that normal hydraulic pressure is maintained in the supply line 15 during frame and dump operations, and also during bucket rocking operations. However, while the LS signal from the shuttle valve 31 is effective in maintaining the supply pressure of the bucket 2 during normal frame and dumping movements, as discussed further below, it has been found that a constant LS signal, for example from the shuttle valve 28, applied according to the invention, more reliably holds the unloading valve 21 in the closed position during bucket rocking operations.

[0062] The control system 20 may include a pressure reducing valve 32 for the LS network and many other conventional components, although not all of them are shown, but these will be apparent to those skilled in the art.

[0063] Industrial applicability

[0064] This novel control system can be applied to any working machine with a tilting bucket operated by a hydraulic pump equipped with an unloading valve, but it is particularly useful in machines with fixed displacement pumps because the unloading valve allows the pump to be driven at a constant speed (and therefore a constant output flow rate), which is controlled by the speed of the prime mover and independent of fluctuations in the demand for hydraulic power, resulting in a simple system. When the unloading valve is closed, the pump's torque reaction increases, causing the prime mover to generate more power to maintain its controlled speed.

[0065] This invention recognizes that, in practice, the rapid reversal of the frame-dump-frame-dump command does not allow sufficient time for the LS signal at the unloading valve to rise to its full amplitude on each cycle. Furthermore, the unloading valve lags behind the signal, and the main supply pressure lags behind the unloading valve. This lag in the hydraulic control system thus results in a damped response at the unloading valve, and further damping of the fluctuating main supply pressure in response to rapid fluctuations in the signal from the joystick or bucket rocking control. Because the pump cannot maintain normal operating pressure in the main supply line, the bucket actuator, or each bucket actuator, responds much slower to fluctuating bucket rocking commands than to continuous frame or dump commands. Therefore, the operator may be frustrated by the insufficiently powerful response of the bucket.

[0066] By maintaining a constant pressure signal in the load sensing circuit to keep the unloading valve constantly closed during the duration of the bucket rocking operation, the pump operates at normal operating pressure in the supply line while supplying the flow required by the bucket control valve to switch the bucket between frame and dump positions. The more constant supply pressure allows the bucket actuator, or each bucket actuator, to move at normal operating speed, resulting in faster bucket movement between frame and dump positions—that is, a more vigorous rocking motion—and thus more efficient removal of debris from the bucket.

[0067] Alternatively, a constant pressure signal can be applied by hydraulically supplying another (second) actuator to hold the bucket in its limit position during yaw operations. Since the second actuator is held in its limit position, the constant pressure does not result in work being done, but rather has the effect of increasing the LS pressure. In this way, a constant pressure signal can be generated with few or no additional valve components, thus simplifying the system.

[0068] By selecting the actuator of the coupling mechanism that locks the bucket to its mount as a second actuator, the applied pressure can advantageously be used to constantly push the coupling mechanism to the locked position during bucket rocking operations. This allows the coupling mechanism to hold the bucket more firmly to the mount during bucket rocking operations, which helps prevent destructive impacts between components.

[0069] Excavators or other working machinery include a tilting bucket operable by a hydraulic actuator, controlled by a bucket control valve in response to a control signal including a bucket tilting control signal that, during bucket tilting operation, causes the bucket to repeatedly move along the frame and tilting direction to agitate debris from the bucket. The actuator is powered by pressure from a hydraulic pump, and the control system includes an unloading valve to release pressure from the supply line to unload the pump when power is not required. The control system is arranged to maintain a constant pressure signal in the load sensing line so as to keep the unloading valve constantly closed during the duration of the bucket tilting operation. This can be achieved by pressurizing the actuator of a quick-connect coupling to lock the bucket onto the machinery.

[0070] Many modifications may be made within the scope of the claims.

[0071] Reference numbers and characters provided in parentheses in the claims are purely for ease of reference and should not be construed as limiting features.

Claims

1. A control system for machinery, The machinery includes: A hydraulic pump, used to supply hydraulic pressure to the supply lines; Bucket; At least one bucket actuator, which is hydraulically operable to tilt the bucket between an upward-facing frame position and a downward-facing dumping position; as well as At least one user controller, which is user-operable to generate control signals, including bucket oscillation control signals; The control system includes: An unloading valve having an unloading valve actuator, the unloading valve being openable in use to release hydraulic pressure from the supply line to unload the hydraulic pump, and the unloading valve being closed by the unloading valve actuator; A load sensing circuit is arranged to apply a pressure signal to the unloading valve actuator in response to a demand for hydraulic power to close the unloading valve and thus maintain hydraulic pressure in the supply line; as well as A bucket control valve, which is operable in use by the control signal to apply the hydraulic pressure from the supply line to the at least one bucket actuator; The bucket control valve is operable in use to cause the at least one bucket actuator to perform a bucket rocking operation in response to the bucket rocking control signal. The bucket rocking operation is a repetitive movement of the bucket alternately toward the frame position and the dumping position to rock debris from the bucket. The control system is configured to maintain a constant pressure signal in the load sensing circuit so as to keep the unloading valve constantly closed during the duration of the bucket rocking operation.

2. The control system as described in claim 1, wherein, The bucket rocking control signal consists of a series of alternating control signals, which are generated by the user through repeated operations controlled by at least one user. Furthermore, the control system is configured to maintain the constant pressure signal in the load sensing circuit in response to the repetition of the alternating control signal at a frequency above a threshold frequency.

3. The control system as described in claim 2, wherein, The alternating control signal is an electrical signal, and the control system includes an electronic controller configured to monitor the electrical signal and determine whether the electrical signal repeats at a frequency higher than the threshold frequency.

4. A machine comprising: A hydraulic pump, used to supply hydraulic pressure to the supply lines; Bucket; At least one bucket actuator, which is hydraulically operable to tilt the bucket between an upward-facing frame position and a downward-facing dumping position; At least one user controller, user-operable to generate control signals, said control signals including bucket oscillation control signals; and The control system according to claim 1, claim 2, or claim 3.

5. The machine as claimed in claim 4, wherein the hydraulic pump is a fixed displacement pump.

6. The machine of claim 4, further comprising at least one second actuator operable by hydraulic pressure. The control system further includes a second actuator control valve; The second actuator control valve is operable to apply hydraulic pressure from the supply line to the at least one second actuator; The load sensing circuit is arranged to apply the hydraulic pressure as the pressure signal to the unloading valve actuator when applied to the at least one second actuator; The control system is configured to operate the second actuator control valve to constantly apply hydraulic pressure from the supply line to the at least one second actuator during the duration of the bucket rocking operation, and to apply pressure as a pressure signal to the unloading valve actuator via the load sensing line.

7. The machine as claimed in claim 6, further comprising: Mounting components, and Connecting mechanism; A bucket that is detachably connected to the mounting; The at least one second actuator is operable to selectively move the coupling mechanism between a locked position and a released position, wherein in the locked position the bucket is locked to the mount via the coupling mechanism, and in the released position the bucket is unlocked from the mount. The control system is configured to operate the second actuator control valve to apply hydraulic pressure from the supply line to the at least one second actuator to constantly push the coupling mechanism to the locked position during the duration of the bucket rocking operation.

8. A method for controlling machinery, The machinery includes: A hydraulic pump, used to supply hydraulic pressure to the supply lines; Bucket; At least one bucket actuator, which is hydraulically operable to tilt the bucket between an upward-facing frame position and a downward-facing dumping position; At least one user controller, which is user-operable to generate control signals, including bucket oscillation control signals; as well as The control system includes: An unloading valve having an unloading valve actuator, the unloading valve being openable in use to release hydraulic pressure from the supply line to unload the hydraulic pump, and the unloading valve being closed by the unloading valve actuator; A load sensing circuit, configured to apply a pressure signal to the unloading valve actuator in response to a demand for hydraulic power to close the unloading valve, thereby maintaining hydraulic pressure in the supply line; and A bucket control valve, which is operable in use by the control signal to apply the hydraulic pressure from the supply line to the at least one bucket actuator; The method includes: Operate the bucket control valve to cause the at least one bucket actuator to perform a bucket rocking operation in response to the bucket rocking control signal. The bucket rocking operation is a repetitive movement of the bucket alternately toward the frame position and the dumping position to agitate debris from the bucket. A constant pressure signal is maintained in the load sensing circuit so that the unloading valve is kept constantly closed during the duration of the bucket rocking operation.

9. The method of claim 8, wherein, The bucket rocking control signal consists of a series of alternating control signals, which are generated by the user through repeated operations controlled by at least one user. And in response to repeating the alternating control signal at a frequency higher than a threshold frequency, the constant pressure signal is maintained in the load sensing circuit.

10. The method of claim 8 or claim 9, wherein: The machine further includes at least one second actuator operable by the hydraulic pressure. Furthermore, the control system further includes a second actuator control valve; The second actuator control valve is operable to apply hydraulic pressure from the supply line to the at least one second actuator; The load sensing circuit is arranged to apply the hydraulic pressure as the pressure signal to the unloading valve actuator when applied to the at least one second actuator; The method further includes: The second actuator control valve is operated to apply hydraulic pressure from the supply line to the at least one second actuator constantly during the duration of the bucket rocking operation, and to the unloading valve actuator as the pressure signal via the load sensing line.

11. The method of claim 10, wherein the machinery further comprises Mounting components, and Connecting mechanism; A bucket that is detachably connected to the mounting; The at least one second actuator is operable to selectively move the coupling mechanism between a locked position and a released position, wherein in the locked position the bucket is locked to the mount via the coupling mechanism, and in the released position the bucket is unlocked from the mount. The method further includes: Operate the second actuator control valve to apply hydraulic pressure from the supply line to the at least one second actuator to constantly push the coupling mechanism to the locked position during the duration of the bucket rocking operation.

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