Abstract:
A fluid system for use with a machine that employs an actuator, that provides for rapid shaking of an implement. The fluid system includes a source for providing fluid flow to the actuator and an operator input device for enabling an operator to control the movement of the implement by inputting a plurality of commands that specify movement of the implement. A controller is provided for monitoring the commands received from the operator input device and entering a mode for controlling the displacement of the source when the controller detects a pattern of commands that indicates an operator-request for rapid movement of the implement.

Description:
TECHNICAL FIELD 
       [0001]    This patent disclosure relates generally to a hydraulic system and, more particularly, to a hydraulic system for use in a machine that employs an implement. 
       BACKGROUND 
       [0002]    Many machines use hydraulic actuators to accomplish a variety of tasks, such as moving an implement. Examples of such machines include, without limitation, dozers, loaders, excavators, motor graders, and other types of heavy machinery. The hydraulic actuators in such machines are linked via fluid flow lines to a pump associated with the machine to provide pressurized fluid to the hydraulic actuators. Chambers within the various actuators receive the pressurized fluid in controlled flow rates in response to operator demands or other signals. The pump can be a load-sense hydraulic pump that, in response to the magnitude of the load acting on the implement, automatically varies the flow rate of the pressurized fluid. For example, when the implement encounters a heavy load, the load-sense hydraulic pump provides a correspondingly high flow rate to the hydraulic actuators. Likewise, when the implement encounters a small or light load, or when no load acts on the implement, the load-sense hydraulic pump provides a correspondingly low flow rate to the hydraulic actuators. 
         [0003]    Oftentimes, after completing a task and when no load is acting on the implement, an operator may desire to dislodge dirt, mud, clay, or debris from the implement. To do so, the operator may quickly cycle a control lever back and forth, causing the hydraulic actuators to expand and retract, thereby moving the implement back and forth in rapid succession. This is sometimes referred to as rapid shakeout, or rapid sharing of the implement. However, because rapid shakeout is desired and typically occurs when no load is acting on the implement, e.g., when the bucket is substantially empty and when the load-sense pump is providing pressurized fluid to the actuators at a low flow rate, the actuators can respond slowly to the operator&#39;s commands. 
         [0004]    Several known hydraulic systems having a load-sense pump have been adapted for accommodating rapid shakeout. One exemplary fluid system is disclosed in U.S. Pat. No. 5,235,809 for a Hydraulic Circuit for Shaking a Bucket on a Vehicle, filed on Sep. 9, 1991, and issued to Robert G. Farrell on Aug. 17, 1993 (“Farrell”). Fluid systems, such as disclosed in Farrell, include an implement such as a bucket operated by a hydraulic actuator, a directional valve for controlling fluid flow from a load sensing variable displacement pump, and a hydraulic bucket shake circuit. In this type of system, when an operator desires a rapid shakeout, the operator manually activates the hydraulic bucket shale circuit, which forces the pump to a maximum displacement condition. In this condition, the pump provides standby pressure and fluid flow to the hydraulic actuator by way of the directional valve so that the hydraulic actuator can rapidly expand and retract to rapidly shaking the bucket. However, it is a shortcoming to this system that manual activation is required for operation of the hydraulic bucket shake circuit. An additional shortcoming is that the hydraulic bucket shake circuit is a binary circuit that is either off or on for forcing the pump to a maximum displacement condition. This design can waste fuel and subjects the machine, including the pump and the engine, to unnecessary wear. 
         [0005]    It should be appreciated that the foregoing background discussion is intended solely to aid the reader. It is not intended to limit the disclosure or claims, and thus should not be taken to indicate that any particular element of a prior system is unsuitable for use, nor is it intended to indicate any element to be essential in implementing the examples described herein, or similar examples. 
       BRIEF SUMMARY 
       [0006]    The disclosure describes, in one aspect, a fluid system for use with a machine that employs an actuator that provides for rapid shaking of an implement. The fluid system includes a source for providing fluid flow to the actuator and an operator input device for enabling an operator to control the movement of the implement by inputting a plurality of commands that specify movement of the implement. A controller is provided for monitoring the commands received from the operator input device and entering a mode for controlling the displacement of the source when the controller detects a pattern of commands that indicates an operator-request for rapid movement of the implement. 
         [0007]    The disclosure describes, in another aspect, a method of controlling the displacement of a source in a machine for providing a fluid flow to an actuator that provides for rapid movement of an implement. The method includes establishing an indicator characterized by a pattern of input commands that indicate a request for rapid movement of the implement. The method also includes monitoring a user-input device for the indicator and, after identifying the indicator, initiating a mode to control the displacement of the source for providing the fluid flow to the actuator that provides for rapid movement of the implement. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a schematic side view of an exemplary machine; 
           [0009]      FIG. 2  is a schematic illustrating an exemplary hydraulic system for use in a machine such as illustrated in  FIG. 1 ; 
           [0010]      FIG. 3  is a graph illustrating an exemplary mode executed by a controller of the hydraulic system of  FIG. 2 ; and 
           [0011]      FIG. 4  is a graph illustrating another exemplary mode executed by the controller of the hydraulic system of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    This disclosure relates to a system and method for controlling a flow of hydraulic fluid in a hydraulic system of a machine. In particular, a controller applies one or more modes to control a rate of flow of hydraulic fluid to an actuator in the machine when an operator requests rapid shaking of an implement. This rapid shaking can, for example, dislodge mud, dirt, clay or debris from the implement. 
         [0013]      FIG. 1  illustrates an exemplary machine  10 . The machine  10  may be a fixed or mobile machine that performs an operation associated with an industry such as, for example mining, construction, farming, or transportation. For example, the machine  10  may be an earth moving machine such as an excavator, a dozer, a loader, a backhoe, a motor grader, or any other earth moving machine. The machine  10  may include a linkage system  12 , an implement  14  attachable to linkage system  12 , one or more hydraulic actuators  16   a - c  interconnecting the linkage system  12 , an operator interface  18 , a power source  20 , and at least one traction device  22 . 
         [0014]    The linkage system  12  may include any structural unit that supports movement of the implement  14 . The linkage system  12  may include, for example, a stationary base frame  24 , a boom  26 , and a stick  28 . The boom  26  may be pivotally connected to the frame  24 , while the stick  28  may be pivotally connected to the boom  26  at a joint  30 . The implement  14  may pivotally connect to the stick  28  at a joint  32 . It is contemplated that the linkage system may alternatively include a different configuration and/or number of linkage members than the system depicted in  FIG. 1 . 
         [0015]    Numerous different implements  14  may be attachable to the stick  28  and controllable via the operator interface  18 . The implement  14  may include any device used to perform a particular task such as, for example, a bucket, a fork arrangement, a blade, a shovel, a ripper, a dump bed, a broom, a snow blower, a propelling device, a cutting device, a grasping device, or any other task-performing device known in the art. The implement  14  may be configured to pivot, rotate, slide, swing, lift, or move relative to machine  10  in any manner known in the art. 
         [0016]    The operator interface  18  may be configured to receive input from an operator indicative of a desired movement of the machine  10 , including the implement  14 . More particularly, the operator interface  18  may include an operator interface device  34  such as, for example, a multi-axis joystick. The operator interface device  34  may be a proportional-type controller configured to position and/or orient the implement  14  and to produce an interface device position signal indicative of a desired movement of the implement  14 . It is contemplated that additional and/or different operator interface devices may be included within operator interface  18  such as, for example, wheels, knobs, push-pull devices, switches, pedals, and other operator interface devices known in the art. 
         [0017]    The power source  20  may be an engine such as, for example, a diesel engine, a gasoline engine, a gaseous fuel-power engine such as a natural gas engine, or any other engine known in the art. It is contemplated that power source  20  may alternatively embody another source of power such as a fuel cell, a power storage device, an electric or hydraulic motor, or another source of power known in the art. 
         [0018]    The traction device  22  may include tracks located on each side of the machine  10 . Alternatively, the traction device  22  may include wheels, belts, or other traction devices. Traction device  22  may or may not be steerable. It is contemplated that if the machine  10  embodies a stationary machine, the traction device  22  may be omitted. 
         [0019]    As illustrated in  FIG. 2 , the machine  10  may include a hydraulic system  40  having a plurality of fluid components that cooperate to move the implement  14 . Specifically, the hydraulic system  40  may include a tank  42  for holding a supply of fluid, and a source  44  configured to pressurize the fluid and to provide a flow of the pressurized fluid to the hydraulic actuators  16   a - c . While  FIG. 1  depicts three actuators, identified as  16   a ,  16   b , and  16   c , for the purposes of simplicity, the hydraulic schematic of  FIG. 2  depicts only one hydraulic actuator identified as  16 . The hydraulic system  40  may include first and second valves  46 ,  48 . The first valve  46  may be a directional valve  46  associated with each end of the hydraulic actuator  16  for directing the flow of pressurized fluid to the hydraulic actuator  16 . The second valve  48  may be a bypass valve located between the tank  42  and the source  44 . 
         [0020]    The hydraulic system  40  also may include a head-end pressure sensor  50  and a rod-end pressure sensor  52  associated with the hydraulic actuator  16 . The hydraulic system  40  may further include a linkage sensor  54  and a controller  56  in communication with the fluid components of hydraulic system  40  and the operator interface device  34 . It is contemplated that hydraulic system  40  may include additional and/or different components such as, for example, accumulators, restrictive orifices, check valves, pressure relief valves, makeup valves, pressure-balancing passageways, temperature sensors, tool recognition devices, and other components known in the art. 
         [0021]    The tank  42  may be a reservoir configured to hold a supply of fluid. The tank  42  may be in fluid communication with the source  44 , the directional valve  46 , and the bypass valve  48 . The fluid may include, for example, a dedicated hydraulic oil, an engine lubrication oil, a transmission lubrication oil, or any other fluid known in the art. The hydraulic system  40  within the machine  10  may draw fluid from and return fluid to the tank  42 . It is also contemplated that hydraulic system  40  may be connected to multiple separate fluid tanks. 
         [0022]    The source  44  may be configured to produce a flow of pressurized fluid and may include a pump such as, for example, a load-sense variable displacement pump. The source  44  draws fluid from the tank  42  and provides fluid flow to the directional valve  46 , which then directs the fluid flow to the actuator  16 . The source  44  may be drivably connected to the power source  20  of the machine  10  by, for example, a countershaft  58 , a belt, an electrical circuit, or in any other suitable manner. Alternatively, source  44  may be indirectly connected to the power source  20  via a torque converter, a gear box, or in any other manner known in the art. It is contemplated that multiple sources of pressurized fluid may be interconnected to supply pressurized fluid flow to the hydraulic system  40 . 
         [0023]    In operation, the source  44  may be a load-sense pump configured to maintain a constant pressure differential between the pressure indicated by a load sense line  59  and the pressure in a supply line  61 , which fluidly connects the source  44  to the directional valve  46 . For example, the load sense line  59  may extend between the directional valve  46  and the source  44  for transmitting, either electronically or hydro-mechanically, to the source  44  information regarding the magnitude of the load acting on the actuator  16 . It should be appreciated that the load sense line  59  may extend between the actuator  16  and the source  44 . 
         [0024]    For example, in an embodiment, the load sense line  59  transmits a pressure value that represents the magnitude of the load acting on the actuator  16 . When a load having a large magnitude acts on the actuator  16 , the load sense line  59  transmits a correspondingly large pressure value to the source  44 . In response, the displacement of the source  44  increases, thereby increasing the pressure in the supply line  61  so as to maintain the constant pressure differential between the pressure in the supply line  61  and the pressure indicated by the load-sense line  59 . Likewise, when a load having a small magnitude acts on the actuator  16 , the load-sense line  59  transmits a correspondingly small pressure value to the source  44 . In response to the small pressure value, the displacement of the source  44  decreases, thereby decreasing pressure in the supply line  61  so as to maintain the constant pressure differential. 
         [0025]    The hydraulic actuator  16  may be a fluid cylinder that interconnects the implement  14  and linkage system  12 . It is contemplated that hydraulic actuators other than fluid cylinders may alternatively be implemented within hydraulic system  40  such as, for example, hydraulic motors or any other type of hydraulic actuator known in the art. As illustrated in  FIG. 2 , the hydraulic actuator  16  may include a tube  60  and a piston assembly  62  disposed within tube  60 . One of the tube  60  and the piston assembly  62  may be pivotally connected between members of the linkage system  12  and/or implement  14 . The hydraulic actuator  16  may include a first chamber  64  and a second chamber  66  separated by a piston  68 . The first and second chambers  64 ,  66  may be selectively supplied with pressurized fluid from the source  44  and selectively drained of the fluid to cause the piston assembly  62  to displace within tube  60 , thereby changing the effective length of the hydraulic actuator  16 . This expansion and retraction of hydraulic actuator  16  may function to move the implement  14  and linkage system  12 . 
         [0026]    The piston assembly  62 , as shown, includes the piston  68  axially aligned with, and disposed within, the tube  60 , and a piston rod  70  connectable to the frame  24 , the boom  26 , the stick  28 , or the implement  14 . The piston  68  may include a first hydraulic surface  72  and a second hydraulic surface  74  opposite the first hydraulic surface  72 . An imbalance of force caused by fluid pressure on the first and second hydraulic surfaces  72 ,  74  may result in movement of piston assembly  62  within tube  60 . For example, a force on the first hydraulic surface  72  greater than a force on the second hydraulic surface  74  may cause the piston assembly  62  to expand out of the tube  60 , thereby increasing the effective length of the hydraulic actuator  16 . Similarly, when a force on the second hydraulic surface  74  is greater than a force on the first hydraulic surface  72 , the piston assembly  62  may retract within tube  60 , thereby decreasing the effective length of the hydraulic actuator  16 . A flow rate of fluid into and out of the first and second chambers  64 ,  66  may determine the velocity of the hydraulic actuator  16 , while a pressure of the fluid in contact with the first and second hydraulic surfaces  72  and  74  may determine an actuation force of the hydraulic actuator  16 . A sealing member, such as an o-ring, may be connected to the piston  68  to restrict a flow of fluid between an internal wall of the tube  60  and an outer cylindrical surface of the piston  68 . 
         [0027]    The directional valve  46  may be disposed between the source  44  and the actuator  16  and between the tank  42  and the actuator  16 . The directional valve  46  may be configured to regulate the flow of pressurized fluid to and from the first and second chambers  64 ,  66  of the actuator  16  in response to commands from the controller  56 , which receives commands from the operator interface device  34 . The directional valve  46  may move between a first-open position, a closed position, and a second-open position. 
         [0028]    In the first-open position, the directional valve  46  directs fluid from the source  44  to first chamber  64  for expanding the hydraulic actuator  16  and moving the implement  14  in a first direction. When the actuator  16  is expanding, fluid exits the second chamber  66  and flows back to the directional valve  46 , which then directs the fluid back to the tank  42 . In the second-open position, the directional valve  46  directs fluid from the source  44  to the second chamber  66 , thereby retracting the piston assembly  62  into the tube  60  of the actuator  16  and moving the implement  14  in a second direction. The retracting piston assembly  62  forces fluid out of the first chamber  64  and back to the directional valve  46 , which then directs the fluid back to the tank  42 . When in the closed position, the directional valve  46  blocks fluid from flowing from the source  44  to the actuator  16  and from the actuator  16  to the tank  42 . 
         [0029]    In the case where the source  44  is a load-sense pump and when the directional valve  46  is in either the first- or second-open position, more fluid flow is needed from the source  44  to maintain the pressure in the supply line  61 . Accordingly, to maintain the constant pressure differential between the pressure in the supply line  61  and the pressure indicated by the load sense line  59 , the displacement/speed of the source  44  increases so as to provide more fluid flow in the supply line  61  when the directional valve  46  is in either the first- or second-open position. 
         [0030]    The directional valve  46  may include a proportional spring biased mechanism that is solenoid actuated and configured to move the directional valve  46  between the first-open, closed, and second-open positions. The directional valve  46  may be movable to any position between these positions to vary the rate of flow to and from the first and second chambers  64 ,  66  of the actuator  16 , thereby affecting the velocity of actuator  16  and the velocity of the moving implement  14 . It is contemplated that the directional valve  46  may alternatively be hydraulically actuated, mechanically actuated, pneumatically actuated, or actuated in any other suitable manner. 
         [0031]    The bypass valve  48  may be fluidly connected to the supply line  61  for selectively permitting fluid to bypass the directional valve  46  and flow back to the tank  42 . The bypass valve  48  may include a proportional spring biased valve mechanism that is solenoid actuated and configured to move between an open position at which fluid is allowed to flow back to tank  42 , and a closed position at which fluid flow is blocked from flowing back to tank  42 . It is contemplated that bypass valve  48  may alternatively be hydraulically actuated, mechanically actuated, pneumatically actuated, or actuated in any other suitable manner. 
         [0032]    The bypass valve  48  may be movable to any position between the open and closed positions to vary the rate of flow back to tank  42 , thereby affecting the displacement/speed of the source  44 . The rate of flow to tank  42 , which is controlled by the displacement of the bypass valve  48 , is directly proportional to the displacement of the source  44 . For example, in the case where the source  44  is a load-sense pump and when the bypass valve  48  is in the open position for allowing a rate of flow to tank  42 , increased displacement from the source  44  is needed to provide a corresponding increase in the rate of flow in the supply line  61  so as to maintain the constant pressure differential between the pressure in the supply line  61  and the pressure indicated by the load sense line  59 . 
         [0033]    The controller  56  may embody a single microprocessor or multiple microprocessors that include a means for controlling an operation of the hydraulic system  40 . Numerous commercially available microprocessors can be configured to perform the functions of the controller  56 . It should be appreciated that the controller  56  could readily be embodied in a general machine microprocessor capable of controlling numerous machine functions. The controller  56  may include a memory, a secondary storage device, a processor, and any other components for running and executing an application. Various other circuits may be associated with the controller  56  such as power supply circuitry, signal conditioning circuitry, solenoid driver circuitry, and other types of circuitry. 
         [0034]    The controller  56  may be configured to command the bypass valve  48  to proportionally move between the first and second positions for increasing and decreasing the displacement of the source  44 . This may be useful, for example, when the source  44  is a load-sense pump. In such a case, when a load having a small magnitude acts on the implement  14 , the load sense line  59  indicates a correspondingly small pressure. Accordingly, to maintain the constant pressure differential between the pressure in the supply line  61  and the pressure indicated by the load-sense line  59 , the load-sense pump  44  operates at a low displacement. 
         [0035]    This characteristic of load-sense pumps  44  can be disadvantageous because oftentimes, after completing a task and when no load is acting on the implement  14 , an operator may want to rapidly shake the implement  14 , thereby dislodging mud, dirt, clay, or debris from the implement  14 . However, the load-sense pump  44 , which is operating at a low displacement, provides fluid having a low flow rate to the actuator  16 . Because the flow rate of the fluid entering and exiting the first and second chambers  64 ,  66  of the actuator  16  determines the velocity at which actuator  16  expands and retracts, in conditions of low fluid flow rates to the actuator  16 , the actuator  16  may not expand and retract fast enough to rapidly shake the implement  14 . Accordingly, the movements of the implement  14  lag behind the operator&#39;s rapid commands. 
         [0036]    To prevent this lag from occurring when a small-magnitude load acts on the implement  14 , the controller  56 , upon identifying a pattern of input commands that indicate a request for rapid shaking, is configured to automatically initiate a mode for controlling the displacement of the source  44 . For example, the controller  56  may initiate a destroke-reduction mode and/or a rapid-movement mode. 
         [0037]      FIG. 3  provides a graphical illustration of the displacement of various components of the hydraulic system  40  when the controller  56  is operating in the destroke-reduction mode, which is a mode for reducing the destroke rate of the source  44  when an operator is attempting to rapidly shake the implement  14 . At time=0, the operator inputs a command, e.g., the operator moves the joystick, indicating a request for movement of the implement  14 . In response, the controller  56  instructs the directional valve  46  to move from the closed position to one of the first- and second-open positions, thereby increasing the displacement of the source  44  to 100% so as to provide fluid flow to the actuator  16  for moving the implement  14  in a manner consistent with the inputted command. At time=T 1 , the operator retracts the command, e.g., the operator moves the joystick back to a neutral position, thereby indicating a request to discontinue movement of the implement  14 . In response, the controller  56  instructs the direction valve  46  to move back to the closed position. 
         [0038]    Accordingly, within the time elapsed between time=0 and time=T 1 , the operator inputted a pattern of commands indicating a request that the implement  14  move and then discontinue moving. The controller  56  is configured to recognize this pattern of commands as indicating an operator-request for rapid shaking of the implement and, in response, initiate the destroke-reduction mode. It is contemplated that T 1  can be defined according to user preferences. For example, T 1  can be one-quarter or one-half of a second. It is contemplated that that controller  56  can be configured to recognize other patterns of commands as indicating an operator-request for rapid shaking of the implement. 
         [0039]    When operating in the destroke-reduction mode and when the operator inputs a command indicating a request to discontinue movement of the implement  14 , the controller  56  is configured close the directional valve  46  and open the bypass valve  48 . Opening the bypass valve  48  reduces the rate of decrease in the displacement of the source  44  because, in the case where the source  44  is a load-sense pump, the displacement of the source  44  must remain sufficiently high to maintain the pressure differential between the pressure in the supply line  61  and the pressure indicated by the load-sense line  59 . If the bypass valve  48  were not open when the directional valve  46  is closed, the source  44  would be forced to operate at a low displacement for maintaining the constant pressure differential between the pressure in the supply line  61  and the pressure indicated by the load-sense line  59 . This concept is illustrated in  FIG. 3 , where at time=T 1 , the operator inputs a command indicating a request for discontinuing movement of the implement  14 . In response to this command, the source displacement with the controller operated bypass valve  48  decreases to approximately 25%, whereas the source displacement without the controller operated bypass valve  48  decreases to approximately 0%. 
         [0040]    As a result, when the operator inputs a subsequent command indicating a request for movement of the implement  14 , the source displacement with the controller operated bypass valve  48  will obtain 100% displacement in less time than the source displacement without the controller operated bypass valve  48 . This is also illustrated in  FIG. 3 , where at time=T 2 , the operator inputs a command indicating a request for movement of the implement  14  and, in response to this command, the source displacement with the controller operated bypass valve  48  obtains 100% displacement at T 3 , whereas the source  44  displacement without the controller operated bypass valve  48  obtains 100% displacement later, at T 4 . As such, the directional valve  46 , when receiving fluid flow from the source  44  operating in combination with the controller operated bypass valve  48 , is capable of directing fluid flow at a high flow rate between the first and second chambers  64 ,  66  of the actuator  16 , thereby providing rapid back-and-forth movement of the piston  68  and the implement  14 . 
         [0041]    In an embodiment, the controller  56  is configured to operate in a rapid-movement mode which can increase the displacement of the source  44 . The controller  56 , when operating in the rapid-movement mode, is configured to proportionally open the bypass valve  48  to maintain the source  44  at about 50% of the maximum displacement when the operator inputs a command indicating a request that the implement  14  remain stationary, e.g., when the joystick is in the neutral position and when the directional valve  46  is in the closed position. Accordingly, when an operator inputs a pattern of commands indicating a request for rapid shaking of the implement  14 , the source  44 , operating at 50% displacement, can quickly increase to 100% displacement for providing an adequate flow rate of fluid flow in and out of first and second chambers  64  and  66  of the actuator  16 . It is contemplated that the bypass valve  48  may be proportionally opened or closed, e.g., the displacement of the bypass valve may be proportionally increased or decreased, for maintaining the source  44  at a standby displacement of less or more than 50%. 
         [0042]      FIG. 4  provides a graphical illustration of the displacement of various components of the hydraulic system  40  when the controller  56  is operating in the rapid-movement mode. The controller  56  is configured to proportionally open the bypass valve  48  when the directional valve  46  moves to the closed position, e.g., when the implement  14  is stationary. Accordingly, at time=0, when the operator&#39;s command indicates a request that the implement  14  remain stationary, the controller  56  maintains the bypass valve  48  in an open position and the directional valve  46  in a closed position. As shown in  FIG. 4 , at time=0, the open bypass valve  48  forces the source  44  to operate at a displacement of about 50% so as to maintain the constant pressure differential between the pressure in the supply line  61  and the pressure indicated by the load-sense line  59 . Also illustrated in  FIG. 4  is the displacement of the source  44  without the controller  56  operated bypass valve  48 . As shown in  FIG. 4 , without the bypass valve  48 , the displacement of the source  44  at time=0 is approximately 0%. The displacement of the source  44  operating without the bypass valve  48  is low because only a small amount of fluid flow is required to maintain the constant pressure differential when no load is acting on the implement  14  and when the directional valve  46  is in the closed position. 
         [0043]    At time=T 1 , the operator inputs a command indicating a request for movement of the implement  14 . In response, controller  56  moves the directional valve  46  to either the first- or second-open position and moves the bypass valve  48  to the closed position. Closing the bypass valve  48  forces all of the flow in the supply line  61  to the directional valve  46 , which directs the flow to the actuator  16 . Because the source  44  is operating at 50% displacement when the directional valve  46  opens, the source  44  increases to 100% displacement in less time than the source  44  without the controller operated bypass valve  48 . Accordingly, as illustrated in  FIG. 4 , the source  44 , and the actuator  16  which receives fluid flow from the source  44 , are more responsive to operator commands, e.g., commands requesting rapid movement of the implement, when the hydraulic system  40  includes the controller operated bypass valve  48 . 
         [0044]    In operation, the controller  56 , when programmed to operate the bypass valve  48  pursuant to the destroke-reduction mode and/or the rapid-movement mode described herein, causes the source  44  to be capable of quickly providing sufficient rates of fluid flow to rapidly shale the implement  14 . Thus, for example, in the case of an excavator or backhoe having a load-sense pump and a bucket used for moving earth, the excavator or backhoe may, upon the command of an operator and without first having to manually open a binary bypass valve, rapidly shake the bucket at a time when the bucket is substantially empty to dislodge dirt, mud, clay, or debris from the bucket. 
       INDUSTRIAL APPLICABILITY 
       [0045]    The industrial applicability of the system and method described herein will be readily appreciated from the foregoing discussion. A technique is described wherein the rate of flow to an actuator such as for rapid shaking of an implement is controlled to provide an adequate rate of flow to the actuator within a small amount of time. 
         [0046]    The disclosed hydraulic system and method are applicable to any hydraulically actuated machine that includes a fluidly connected hydraulic actuator where it is desirable to provide fluid flow to the actuator for rapidly shaking an implement. The disclosed hydraulic system includes a controller that applies one or more modes to control a rate of flow to the actuator when an operator requests rapid movement of an implement. In this manner, an adequate rate of flow is available for rapid shaking, while minimizing unnecessary and wasteful displacement from a source, such as a pump. 
         [0047]    During operation of the machine  10 , a machine operator manipulates the operator interface device  34  to create a desired rapid shaking of the implement  14 . Throughout this process, the operator interface device  34  generates signals indicative of desired flow rates of fluid supplied to hydraulic actuators  16   a - c  to accomplish the desired shaking. The controller  56 , upon identifying signals indicative of a request for rapid shaking, executes the destroke-reduction mode and/or the rapid-movement mode, as described with reference to  FIGS. 3 and 4 , to provide an adequate rate of flow to the hydraulic actuators  16   a - c  for moving the implement  14  as requested by the operator. 
         [0048]    It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the invention or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the invention generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the invention entirely unless otherwise indicated. 
         [0049]    Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. 
         [0050]    Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.