Abstract:
A work vehicle having an implement, including: a frame; a boom arm assembly connected at one end to the frame; an implement assembly pivotally connected to another end of the boom arm assembly and including the implement; a first hydraulic implement cylinder connected to the implement assembly and positioned to pivotally rotate the implement relative to the boom arm assembly when a piston of the first implement cylinder is extended or retracted, the first hydraulic implement cylinder being connected to a first electrohydraulic valve for activating extension and retraction of the piston of the first implement cylinder; and a controller connected to send control signals to activate the first electrohydraulic valve, wherein the controller sends a series of shaking control signals to alternately extend and retract the first implement cylinder to effect a shaking movement of the implement.

Description:
FIELD OF THE INVENTION 
     The present invention pertains generally to a work vehicle that has a bucket, such as a skid steer loader, and, more particularly to a work vehicle with a bucket shaker to dislodge material from the bucket, if necessary. More particularly, the present invention relates to an improved work vehicle that includes a mechanism for dislodging material from the bucket that provides automatic bucket shaking under the control of an on board computer or microprocessor. 
     BACKGROUND OF THE INVENTION 
     Skid steer loaders (also known as “skidders”) are work vehicles that include four wheels rotatably mounted to a frame, an engine mounted on the frame and connected by a transmission to rotate at least two wheels, a cab compartment mounted on the frame that includes a seat for an operator, manual controls and a display panel disposed in the cab compartment, a boom assembly rotatably mounted on the frame and connected to a pair of hydraulic boom cylinders for moving the boom assembly, and an implement assembly connected to the boom assembly. Typically, one or more hydraulic cylinders are used to manipulate the implement assembly. Preferably, the implement assembly is a bucket assembly, wherein the implement is a bucket and a pair of hydraulic bucket cylinders is used to move the bucket assembly. Other types of work vehicles that are similar to skid steer loaders include tractors and bulldozers. 
     When a skidder is equipped with a loader bucket, the work vehicle is primarily used for digging. One issue that arises during digging operations is that dumping of dirt and other potentially sticky materials such as manure, fertilizers, sand, and the like, from the loader bucket may be incomplete, leaving behind a residue. Consequently, some materials can remain stuck to the inside of the loader bucket. Typically, the operator of the skidder will manipulate the manual controls in the cab compartment to “shake” the loader bucket to assist any material residue to jar loose and fall out of the bucket. This operation entails rapidly moving the manual controls in a reciprocating manner to effect shaking of the bucket. Several problems emerge when shaking is attempted in the above manner. First, the amount of shaking the operator can achieve is limited to the human ability to reciprocate the manual controls to effect a shake. This means that the reciprocating movements have a relatively low frequency and generally a large magnitude so that the shake is suboptimal and it may take some amount of shaking to dislodge sticky material from the loader bucket. Second, the hydraulic circuit of the work vehicle generally includes a valve stack for activating movement of the boom assembly and loader bucket; however, the various solenoid activated spool valves used are relatively sluggish because they respond to analog signals, thereby placing a limitation on the capacity of the hydraulic circuit to shake the boom assembly and loader bucket. Third, such rapid manipulation of the manual controls may overstress the manual controls and render them prone to damage. 
     To operate the hydraulic boom cylinders and the hydraulic bucket cylinders, an operator in the cab manipulates either hand or foot controls. The skid steer loader, or similar work vehicle, includes an electronic control circuit system that includes an onboard computer, microprocessor, or controller. For the purposes of this disclosure, a computer, microprocessor, or controller are considered to be equivalent and interchangeable elements. The onboard computer operates solenoids of electrohydraulic valves that activate the hydraulic boom and the hydraulic bucket cylinders. 
     U.S. patent application Publication US 2001/0007087 A1 to Brandt et al., which is incorporated herein by reference for all that it discloses, teaches a computer based control system for a skid steer loader that includes a computer receiving inputs from a control panel, various sensors, hand grip and foot pedal inputs, and a seat bar sensor. The computer generates outputs to hydraulic actuators and associated valves, and to electromechanical devices. 
     An object of the present invention is to provide an improved electronic control system for a work vehicle, or like machine, having a boom assembly and a loader bucket implement assembly connected to the boom assembly so that the improved electronic control system of the present invention maintains the benefits of the prior art electronic control systems while overcoming at least some of the drawbacks of these prior art control systems. 
     SUMMARY OF THE INVENTION 
     In accordance with the above objectives, the present invention provides, in a first embodiment, a work vehicle having an implement with: (a) a frame; (b) a boom arm assembly connected at one end to the frame; (c) an implement assembly pivotally connected to another end of the boom arm assembly and including the implement; (d) a first hydraulic implement cylinder connected to the implement assembly and positioned to pivotally rotate the implement relative to the boom arm assembly when a piston of the first implement cylinder is extended or retracted, the first hydraulic implement cylinder being connected to a first electrohydraulic valve for activating extension and retraction of the piston of the first implement cylinder; and (e) a controller connected to send control signals to activate the first electrohydraulic valve, wherein the controller sends a series of shaking control signals to alternately extend and retract the first implement cylinder to effect a shaking movement of the implement. 
     In accordance with a second embodiment of the invention, the first embodiment is modified so that the controller operates in a first operational mode and in a second operational mode, wherein the controller generates and sends a first series of control signals to the first electrohydraulic valve when operating in the first operational mode and the controller generates and sends the series of shaking control signals when operating in the second operational mode. 
     In accordance with a third embodiment of the invention, the second embodiment is modified to include a shaking mode activation switch connected to send a command signal to the controller, wherein when the activation switch is engaged the activation switch sends the command signal to the controller and the controller operates in the second mode so long as the controller receives the command signal from the activation switch. 
     In accordance with a fourth embodiment of the invention, the first embodiment is modified so that the first electrohydraulic valve is a cartridge valve having at least one digital coil, and the at least one digital coil is connected to receive control signals from the controller. 
     In accordance with a fifth embodiment of the invention, the first embodiment is modified to include a second hydraulic implement cylinder connected to the implement assembly and positioned to pivotally rotate the implement relative to the boom arm assembly when a piston of the second implement cylinder is extended or retracted, the second hydraulic implement cylinder being connected to the first electrohydraulic valve for activating extension and retraction of the piston of the second implement cylinder and the piston of the first implement cylinder, wherein the controller sends a series of shaking control signals to alternately extend and retract the first implement cylinder and the second implement cylinder to effect a shaking movement of the implement. 
     In accordance with a sixth embodiment of the invention, the first embodiment is modified to include a second hydraulic boom cylinder connected to the boom arm assembly and positioned to move the boom arm assembly relative to the frame of the work vehicle when a piston of the second boom cylinder is extended or retracted, the second hydraulic boom cylinder being connected to a second electrohydraulic valve for activating extension and retraction of the piston of the second boom cylinder, and the controller is connected to send control signals to activate the second electrohydraulic valve, wherein the controller sends control signals to effect movement of the boom assembly. 
     In accordance with a seventh embodiment of the invention, the sixth embodiment is modified so that the second electrohydraulic valve is a cartridge valve having at least one digital coil, and the at least one digital coil is connected to receive control signals from the controller. 
     In an eighth embodiment in accordance with the present invention, the first embodiment is modified so that the implement is a loader bucket. 
     In an ninth embodiment in accordance with the present invention, a work vehicle having an implement comprising: (a) a frame; (b) a boom arm assembly connected at one end to the frame; (c) an implement assembly pivotally connected to another end of the boom arm assembly and including the implement; (d) a first hydraulic boom cylinder connected to the boom arm assembly and positioned to move the boom arm assembly relative to the frame of the work vehicle when a piston of the first boom cylinder is extended or retracted, the first hydraulic boom cylinder being connected to a first electrohydraulic valve for activating extension and retraction of the piston of the first boom cylinder; (e) a first hydraulic implement cylinder connected to the implement assembly and positioned to pivotally rotate the implement relative to the boom arm assembly when a piston of the first implement cylinder is extended or retracted, the first hydraulic implement cylinder being connected to a second electrohydraulic valve for activating extension and retraction of the piston of the first implement cylinder; and (f) a controller connected to send control signals to activate the first electrohydraulic valve and the second electrohydraulic valve, wherein the controller sends a series of shaking control signals to alternately extend and retract one of the first implement cylinder and the first boom cylinder to effect a shaking movement of either the implement or the boom arm assembly and the implement. 
     In accordance with a tenth embodiment of the invention, the ninth embodiment is modified so the controller operates in a first operational mode and in a second operational mode, wherein the controller generates and sends a first series of control signals to the first electrohydraulic valve and the second electrohydraulic valve when operating in the first operational mode and the controller generates and sends the series of shaking control signals when operating in the second operational mode. 
     In accordance with an eleventh embodiment of the invention, the tenth embodiment is further modified to include a shaking mode activation switch connected to send a command signal to the controller, wherein when the activation switch is engaged the activation switch sends the command signal to the controller and the controller operates in the second mode so long as the controller receives the command signal from the activation switch. 
     In accordance with a twelfth embodiment of the invention, the ninth embodiment is modified so each of the first electrohydraulic valve and the second electrohydraulic valve is a cartridge valve having at least one digital coil, and the at least one digital coil is connected to receive control signals from the controller. 
     In accordance with a thirteenth embodiment of the invention, the ninth embodiment is further modified to include a second hydraulic implement cylinder connected to the implement assembly and positioned to move the implement assembly relative to the boom arm assembly when a piston of the second implement cylinder is extended or retracted, the second hydraulic implement cylinder being connected to the second electrohydraulic valve for activating extension and retraction of the piston of the second implement cylinder and the piston of the first implement cylinder, wherein the controller sends a series of shaking control signals to alternately extend and retract the first implement cylinder and the second implement cylinder to effect a shaking movement of the implement. 
     In accordance with a fourteen embodiment of the invention, the ninth embodiment is modified so that the implement is a loader bucket. 
     In a fifteenth embodiment in accordance with the present invention, a method for controlling movement of a boom arm assembly and an implement pivotally connected to the boom arm assembly having the steps of: (a) controlling movement of the boom arm assembly and the implement in a first operational mode using a controller that operates in the first operational mode and in a second operational mode, wherein movement control in the first operational mode effects smooth movements of the boom arm assembly and the implement in accordance with input signals received by the controller from control sensors; (b) switching the operation of the controller from the first operational mode to the second operational mode; (c) controlling movement of the boom arm assembly and the implement in the second operational mode using the controller, wherein movement control in the second operational mode effects shaking movement of the implement relative to the boom arm assembly in accordance with input signals received by the controller from one of the control sensors, wherein the shaking movement occurs about a pivotal connection between the boom arm assembly and the implement. 
     In accordance with a sixteenth embodiment of the invention, the fifteenth embodiment is modified so the one of the control sensors is a hand control sensor that generates first signals proportional to a displacement from a neutral position, and the controller receives the first signals from the hand control sensor, wherein the controller uses the first signals to control the shaking movement of the implement in one of a first shaking mode, a second shaking mode and a third shaking mode. 
     In accordance with a seventeenth embodiment of the invention, the sixteenth embodiment is modified so that in the first shaking mode, the controller controls the shaking movement of the implement so that movement in a dump direction is equal to movement in a curl direction. 
     In accordance with a eighteenth embodiment of the invention, the sixteenth embodiment is further modified so in the second shaking mode, the controller controls the shaking movement of the implement so that movement in a dump direction is greater than movement in a curl direction. 
     In accordance with a nineteenth embodiment of the invention, the sixteenth embodiment is further modified so in the third shaking mode, the controller controls the shaking movement of the implement so that movement in a curl direction is greater than movement in a dump direction. 
    
    
     Further objects, features and advantages of the present invention will become apparent from the Detailed Description of the Preferred Embodiments, which follows, when considered together with the attached drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic side perspective view of a work vehicle having a shaking mechanism in accordance with the present invention with the hydraulically activated movement of the boom assembly being shown in phantom. 
     FIG. 2 is a schematic drawing of the hydraulic circuit component of the shaking mechanism that shakes the boom assembly and the implement. 
     FIG. 3 is a schematic drawing of the interior of the cab compartment carried on the work vehicle. 
     FIG. 4 is a schematic drawing of the electronic control circuit connected to control operation of the hydraulic circuit for a work vehicle in accordance with the present invention. 
     FIG. 5 is a flow chart of operative steps in the method of control of the shaking mechanism of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The machine of the present invention is described with reference to FIGS. 1-4, wherein like numerals indicate like parts. The method of control of the shaking mechanism of the machine of the present invention is described with reference to FIG.  5 . The machine embodiment in accordance with the present invention will be described first to facilitate an easy understanding of the method of shaking control. 
     The machine of the present invention shown in FIG. 1 is a compact work vehicle  10 , such as a skid steer loader or other like work vehicle, that includes a cab compartment  20  on the vehicle. Typically, work vehicle  10  includes a body  12  that is mounted on four wheels  13  (only two shown) that are operably connected to a transmission. The transmission is powered by an engine disposed in engine housing  14  located on the body  12 . One skilled in the art would realize that the work vehicle  10  could be a tracked vehicle, a vehicle mounted on rails, or could be a machine mounted to a stationary frame without departing from the scope of the present invention. 
     Work vehicle  10  includes a boom arm assembly  17  that is pivotally connected to the body  12  at one end, and that is pivotally connected at its opposite end to a work implement  16 , such as a loader bucket, or other suitable tool. As shown in FIG. 1, boom arm assembly  17  can be raised and lowered between a lower position A and an upper position B (shown in phantom) through a range of motion using hydraulic power provided by a pair of hydraulic boom cylinders  19  of a hydraulic circuit  50  (shown in FIG. 2) so that the implement  16  can be used to perform its intended function. Implement  16  rotates about pivot connection  25  of the implement assembly (i.e., implement  16  and pivot connection  25 ). 
     In the exemplary illustration of FIG. 1, implement  16  is shown as a loader bucket and the work vehicle  10  is shown as a skid steer loader. One skilled in the art would realize that implement  16  could be practiced as a snow blade, other digging implement, or other suitable tool and the work vehicle  10  could be practiced as a tractor, bulldozer, or other, like vehicle, without departing from the spirit and scope of the present invention. Work vehicle  10  is shown digging into material M at position A, wherein the boom assembly  17  is in a lowered position. Work vehicle  10  is also shown dumping out the material at position B, wherein the boom assembly is somewhat extended and raised at position B. The present invention is directed to a shaking mechanism for shaking the implement  16 , and optionally the boom arm assembly  17 , as will be described below. 
     The shaking mechanism is constructed so as to operate to shake the implement  16 , and in some cases the boom arm assembly  17  and the implement  16 , when an operator in the cab compartment  20  activates the shaking mechanism by engaging a shaker mode activation switch  80  in the cab. In addition, the shaking mechanism is also constructed so as to operate to shake at least implement  16  in any position within the range of motion of the boom arm assembly  17  and implement  16 . To achieve these features of the present invention, the shaking mechanism includes a hydraulic circuit  50  for moving at least implement  16 , and in some instances boom arm assembly  17 , in a pulsatile, shaking, or reverberating manner. The hydraulic circuit  50  is connected to be electronically controlled by electronic control circuit  90 . Control circuit  90  generates and sends control signals to operate special electronically activated hydraulic cartridge valves of hydraulic circuit  50  to effect pulsation, shaking, or reverberation as will be described below. 
     The hydraulic circuit  50 , as shown in FIG. 2, includes two hydraulic gear pumps  52 ,  54  connected to draw hydraulic fluid from hydraulic fluid reservoir  56  via hydraulic conduit C 1  and to pump hydraulic fluid throughout hydraulic circuit  50 . Preferably, pump  52  is a high flow pump and pump  54  is a low flow pump. High flow pump  52  pumps hydraulic fluid via hydraulic fluid conduit C 2  to a diverter valve  58 . Diverter valve  58  operates to divert hydraulic fluid flow to hydraulic conduit C 3  or to hydraulic drain C 4 . Hydraulic fluid flowing through conduit C 3  is used to activate auxiliary valve stack  60 , such as would be used to operate an auxiliary hydraulic device (not shown) via hydraulic output conduit C 6  and check valve  61 , and hydraulic drain conduit C 7  and check valve  62 , and/or to activate implement valve stack  70  via hydraulic conduit C 5 . In the practice of the present invention, auxiliary valve stack  60 , conduits C 6 , C 7 , and check valves  61 ,  62  are optional features that can be omitted without departing from the scope and spirit of the invention. In the case where valve stack  60 , conduits C 6 , C 7 , and check valves  61 ,  62  are omitted, conduits C 3  and C 5  are constructed to be directly contiguous conduits. 
     In either case, whether hydraulic circuit  50  includes the optional structures or not, conduit C 5  provides hydraulic fluid flow to implement valve stack  70 . Implement valve stack  70  incorporates auxiliary valve  72 , implement valve  74 , boom valve  76 , accumulator  75 , inlet valve circuit  77 , and float circuit  78 . Accumulator  75  and inlet valve circuit  77  are connected so as to provide a pilot pressure when the work vehicle  10  is off. Float circuit  78  is provided to allow the boom arm assembly  17  to “float” in a conventional manner. 
     Each valve  72 ,  74 , and  76  is a digital coil operated, spring return-to-center, hydraulic 4/3 cartridge valve, wherein each valve is electrically connected via the digital coil or coils to electronic control circuit  90 . Each digital coil responds to activating digital electronic pulse signals with modulation generated by the controller  110  of control circuit  90 , which gives these cartridge valves the capability to rapidly oscillate. Standard solenoid activated spool valves, in comparison, operate in response to electronic analog signals and do not have the capacity to rapidly oscillate as quickly as the digital coil operated cartridge valves can. Cartridge valves  72 ,  74 , and  76  also share a common hydraulic drain conduit C 9  that drains to reservoir  56 . Furthermore, excess hydraulic fluid flow to the implement valve stack  70  can return to reservoir  56  via hydraulic fluid conduits C 8  and C 4 . 
     Activation of auxiliary cartridge valve  72  serves to provide hydraulic fluid to hydraulic conduit CIO and check valve  71 , which can be connected to provide hydraulic fluid for activating an auxiliary device such as an auger drill. Hydraulic fluid drains back from the auxiliary device via check valve  73  and hydraulic conduit C 11  to auxiliary cartridge valve  72  before draining back to reservoir  56  via conduits C 8  and C 4 . An oil filtration and cooling circuit  57  is connected along conduit C 4  so as to filter and cool the hydraulic fluid returning to reservoir  56 . 
     Activation of implement cartridge valve  74  serves to provide hydraulic fluid to hydraulic conduit C 12  to activate hydraulic implement cylinders  18 . Activation of implement cylinders  18  results in movement of pistons  21 , thereby effecting rotational motion of implement  16  about its pivotal connection  25  to boom arm assembly  17 . Hydraulic fluid drains back from implement cylinders  18  via hydraulic conduit C 13  to implement cartridge valve  74  before draining back to reservoir  56  via conduits C 8  and C 4 . 
     Activation of boom cartridge valve  76  serves to provide hydraulic fluid to hydraulic conduit C 14  to activate hydraulic boom cylinders  19 . Activation of boom cylinders  19  results in movement of pistons  23 , thereby effecting motion of boom assembly  17  such as shown in FIG.  1 . Hydraulic fluid drains back from implement cylinders  19  via hydraulic conduit C 15  to boom cartridge valve  76  before draining back to reservoir  56  via conduits C 8  and C 4 . 
     Hydraulic circuit  50  also includes low flow pump  54  connected to provide hydraulic fluid to conduit C 3  via hydraulic conduit C 16 . Low flow pump  54  provides much of the hydraulic fluid flow needed to activate auxiliary stack  60  and implement valve stack  70 ; however, when much higher flows are needed high flow pump  52  is activated to provide the additional hydraulic flow. 
     Next, the electronic control circuit  90  will be described. FIG. 4 illustrates electrical connections between the various components of the electronic control circuit  90  in accordance with the present invention. Electronic control circuit  90  is carried by the work vehicle  10  and includes an on board controlling microprocessor (also referred to as the “controller”)  110  connected to exchange data with a memory storage device  111 . Preferably, memory storage device  111  is a non-volatile memory that stores the neutral positions of the operator&#39;s manual controls, such as foot control pedals  55  and the hand controls  65 , and other data as described below. Although controller  110  and memory storage device  111  are preferably separate structures, controller  110  can be constructed to incorporate the memory storage device without departing from the scope of the invention. 
     Controller  110  is connected to receive electronic signal inputs from the following devices: operator “seat belt switch and seat switch” circuit  120 , right hand stick implement control and position sensor  122 , left hand stick boom control and position sensor  124 , right foot pedal implement control and position sensor  126 , left foot pedal boom control and position sensor  128 , hand/foot controls selector switch  132 , vehicle tilt sensor  134 , implement leveler mode selection switch  136 , boom position sensor  140 , implement angle position sensor  142 , and shaker mode activation switch  80 . Although many different types of controllers are suitable for use as the controller  110  in system  90  of the present invention, microcontroller C167CR manufactured by Infineon Technologies AG (Germany) is particularly well suited for use in the present system environment. 
     Controller  110  is connected to receive an enabling signal from “seat belt switch and seat switch” circuit  120  that incorporates a seat switch  24  and a seat belt switch  26  as part of seat  22 , such as disclosed in U.S. Pat. No. 4,871,044 to Strosser et al, which is incorporated herein by reference for all it discloses. Seat belt switch  26  includes male seat belt fastener  28  and female seat belt fastener  30 . Specifically, controller  110  is prevented from generating and/or sending activation control signals to activate digital coil controlled hydraulic cartridge valves  74  and  76  for activating hydraulic cylinders  18  and  19 , respectively, until the controller has received the enabling signal from the “seat belt switch and seat switch” circuit  120 . 
     Control and position sensors  122 ,  124 ,  126 , and  128  respectively sense the position of a right hand manual control  65 , a left hand manual control (not shown), a right foot pedal manual control  55  and a left foot pedal manual control (not shown), and each sensor sends a respective data signal to controller  110  indicating the position and rate of change of position of the corresponding manual control from its neutral position. Controller  110  processes this information and generates a first set of digitally modulated control signals that are sent to the electrical digital coils of hydraulic cartridge valves  74  and  76  to operate hydraulic cylinders  18  and  19  in proportion to the deviation of right and left manual controls from a neutral position. In other words, the rate of change of position of implement  16  and boom arm assembly  17  is determined by the position of the right and left manual controls, respectively, be they hand manual controls  65  or foot pedal manual controls  55 . 
     Controller  110  is connected to receive a selection signal from hand/foot control selector switch  132 , wherein the selection signal is used to determine whether controller  110  will be enabled to process manual control input signals received only from the hand controls  65  or only from the foot pedal controls  55 . In other words, electronic control circuit  90  utilizes signal input from either hand control sensors  122 ,  124  or foot pedal sensors  126 ,  128 , but at any one time circuit  90  can not utilize signal input from all four sensors  122 ,  124 ,  126 ,  128 . Circuit  90  is constructed to utilize signal inputs from only one pair of these control and position sensors at a time, being either right and left hand control and position sensors  122 ,  124  or right and left foot pedal control and position sensors  126 ,  128 , and to generate and send control signals to the digital coils of cartridge valves  74  and  76  in response to receiving the control and position sensor signal input. 
     Controller  110  may also be connected to receive data signal input from other sensors such as vehicle tilt sensor  134 , boom position sensor  140 , and implement angle position sensor  142 . Controller  110  utilizes these position data signals for various implement  16  and boom assembly  17  automatic positioning functions as may be programmed into the controller. For example, controller  110  can be connected to receive a mode selection signal from implement leveler mode selection switch  136 . The mode selection signal would instruct controller  110  to operate in one of several implement self-leveling modes programmed into the controller. Some of the implement self-leveling modes might require data signal input from sensors  134 ,  140 , and/or  142  to operate properly. 
     In accordance with the present invention, controller  110  is preprogrammed to generate digitally modulated output control signals to selectively activate the digital coils of cartridge valves  72 ,  74  and  76  to effect smooth hydraulic flow or pulsatile, shaking, or reverberating hydraulic fluid flow upon command. More particularly, the digital coils of cartridge valve  74  and cartridge valve  76  are controlled by a first set of control signals generated by controller  110  so as to effect smooth hydraulic fluid flow to hydraulic implement cylinders  18  and hydraulic boom assembly cylinders  19  when the controller  110  is operating in a first operational mode, corresponding to the normal operation of the implement and the boom assembly. However, upon receiving an activating command signal, controller  110  switches its mode of operation to a second operational mode corresponding to controlling cartridge valves  74  and  76  to effect pulsatile, shaking or reverberating hydraulic fluid flow so that at least the implement  16 , and in some embodiments boom arm assembly  17 , is moved in a pulsatile, shaking or reverberating manner. 
     The activating command signal instructing controller  110  to selectively control cartridge valve  74 , and/or possibly cartridge valve  76 , to effect pulsatile, shaking or reverberating hydraulic fluid flow, originates from shaking mode activation switch  80 . Preferably, shaking mode activation switch  80  is located on the right hand manual control  65  as shown in FIG. 2, and is connected to send the activating command signal to controller  110 . Simply stated, as long as switch  80  is depressed, switch  80  sends a shaking mode activating signal to controller  110 , and the controller responds by generating a second set of digital control signals (also known as the “shaking signals”) modulated in accordance with the program of the controller  110 . The shaking signals are sent to the electronic digital coils of hydraulic cartridge valve  74 , and/or possibly hydraulic cartridge valve  76 , with a modulation that operates hydraulic cylinders  18 , and/or possibly hydraulic cylinders  19 , in a pulsatile, shaking or reverberating manner, hereafter also referred to as operating in the “implement shaking mode.” When the hydraulic cylinders  18 , and/or possibly hydraulic cylinders  19 , are operated in the implement shaking mode, the pistons  21  and  23 , respectively, move alternately between extension and retraction in short, rapid, pulsatile, shaking or reverberating movements to effect cyclic pulsatile, shaking or reverberating movement of the implement  16  and/or boom assembly  17 . 
     When in the implement shaking mode of the preferred embodiment of the present invention, controller  110  sends the shaking signals only to cartridge valve  74  so that only implement  16  is shaked. However, one of ordinary skill in the art would appreciate that, when in the implement shaking mode, controller  110  could be programmed to send the shaking signals only to cartridge valve  76  so that only the boom assembly  17  is directly shaken without departing from the spirit and scope of the present invention. In this case, implement  16  gets shaken along with the boom arm assembly  17  because it is carried by the boom arm assembly  17 . One of ordinary skill in the art would also appreciate that, when in the implement shaking mode, controller  110  could be programmed to send the shaking signals to both cartridge valve  74  and cartridge valve  76  simultaneously, thereby directly shaking both implement  16  and boom assembly  17  without departing from the spirit and scope of the present invention. 
     Controller  110  is also connected to send output signals to indicators  139  of a status display  138  of a Total Control System display  85 , such as might be located in the cab compartment  20  of the work vehicle  10 . Indicators  139  would indicate various conditions of the work vehicle  10 , such as the condition of the “seat belt switch and seat switch” circuit  120 , any implement self-leveling mode in effect, and whether hand or foot pedal manual controls are enabled. 
     As described above, the work vehicle  10  in accordance with the present invention has an implement shaking mechanism that includes electronic control circuit  90  that is operable in an implement shaking mode activated by a shaking mode switch  80 . When control circuit  90  is operating in the implement shaking mode, it generates modulated digital shaking signals that are sent to the digital coils of cartridge valve  74 , and/or possibly cartridge valve  76 , thereby operating the activated cartridge valve or valves to effect pulsatile, shaking, or reverberating movement of each valve&#39;s respective piston. Each piston, moving to extend and retract in a rapid pulsatile, shaking, or reverberating manner, likewise moves at least the implement  16  in a shaking manner. In some embodiments, both the implement  16  and the boom assembly  17  could be shaken together. 
     The most effective and efficient shaking mechanism embodiment in accordance with the present invention is the shaking mechanism embodiment programmed to shake the implement  16  and not the boom arm assembly  17 . This is because the implement  16  is smaller than the boom arm assembly  17  and is relatively easy to oscillate about pivot connection  25 . The method of controlling the shaking mechanism, in accordance with this preferred implement shaking embodiment of the present invention, is diagramed in the flow chart shown in FIG.  5 . However, the method outlined in FIG. 5 could be modified to shake the boom arm assembly  17  or both the boom arm assembly and the implement  16 . 
     Referring to FIG. 5, the start condition  200  is the normal operating condition, or first operational mode, of the shaking mechanism. In the first operational mode, controller  110  generates and sends a first series of digital signals to cartridge valves  74  and  75  modulated to effect smooth movements of the boom arm assembly  17  and implement  16  in accordance with input signals from hand control sensors  122 ,  124  or foot pedal control sensors  126 ,  128 , and any other enabled input signals for effecting boom arm assembly and implement movement control (i.e., signal input from vehicle tilt sensor  134 , boom position sensor  140 , implement angle position sensor  142 , and etc.). 
     In the next step  202 , controller  110  determines if the shaker mechanism should be enabled to operate in the second operational mode, also referred to as the implement shaking mode. In the implement shaking mode, controller  110  generates and sends a series of second digitally modulated shaking control signals to at least the digital coils of cartridge valve  74  so as to effect rapid pulsating, shaking, or reverberating movements of implement  16 . In the shaker mechanism enabling step  202 , the shaking mode switch  80  either is engaged or not engaged. When switch  80  is engaged, switch  80  sends a command signal to controller  110  that directs the controller to generate and send the shaking control signals, thereby enabling or activating the implement shaking mode and the method moves to step  206 . When switch  80  is not engaged, no command signal is sent from switch  80  to controller  110 . Under this condition, the method has moved to step  204  wherein controller  110  continues to operate the shaking mechanism in the first operational mode. 
     When the method algorithm moves to step  206 , controller  110  operates to disable the normal implement control algorithm, being the first operational mode, as the controller operates to enable the control subroutine of the second operational mode. In the second operational mode, the method moves from step  206  to step  208 . 
     In step  208 , controller  110  determines whether the hand controls  65  or the foot pedal controls  55  are in the neutral position depending upon which set of manual controls have been selected for and enabled by the hand/foot controls selector switch  132 , because only one set of manual controls is enabled at any one time. In the case where the hand controls  65  are enabled, controller  110  determines from signals provided by the right hand stick implement control and position sensor  122  if the right hand control  65  is in the neutral position. When this condition is present, the method moves to step  210 . 
     In step  210 , the program of the controller  110  instructs the controller to prepare to generate and send modulated digital signals to the digital coils of cartridge valve  74  so that the implement  16  will shake in a first shaking mode. In the first shaking mode, the dump time and the curl time are set to be equal (e.g., dump time=curl time=250 msec). In this context, implement  16  is said to be moving in the “dump direction” D when it is being rotated towards the ground G as indicated in FIG.  1 . Also in this context, implement  16  is said to be moving in the “curl direction” C when it is being rotated away from the ground G as indicated in FIG.  1 . Thus, the “dump time” is defined as the length of time that the implement  16  is moved in the dump direction and the “curl time” is the length of time implement  16  is moved in the curl direction. So, when the enabled right hand manual control  65  is in the neutral position, the method is in step  210  and controller  110  operates the shaking mechanism to shake implement  16  with equal oscillations in the dump direction and the curl direction. Consequently, the implement  16  will shake around some neutral position. 
     However, when right hand manual control  65  is not in the neutral position, the method moves from step  208  to step  212 . In step  212 , the controller receives signals provided by the right hand stick implement control and position sensor  122  and determines if the right hand manual control  65  is in a right or “dump” position. When this condition is present, the method moves to step  214 . When this condition is not met, the right hand manual control  65  must be in a left or “curl” position and the method moves to step  216 . 
     In step  214 , the program of the controller  110  instructs the controller to prepare to generate and send modulated digital signals to the digital coils of cartridge valve  74  so that the implement  16  will shake in a second shaking mode. In the second shaking mode, the dump time is calculated from a table value that is based upon the dump position of the right hand manual control  65 , which is the right-ward displacement of the right hand manual control from the neutral position. The curl time follows from the following equation: curl time=500 msec-dump time. 
     In step  216 , the program of the controller  110  instructs the controller to prepare to generate and send modulated digital signals to the digital coils of cartridge valve  74  so that the implement  16  will shake in a third shaking mode. In the third shaking mode, the dump time is calculated from a table value that is based upon the curl position of the right hand manual control  65 , which is the left-ward displacement of the right hand manual control from the neutral position. The dump time follows from the following equation: dump time=500 msec-curl time. 
     The method moves to step  218  from any one of steps  210 ,  214  and  216 . In step  218 , controller  110  operates to generate and send the appropriately modulated digital signals to the digital coils of cartridge valve  74  so that the implement  16  will shake in one of the first shaking mode, the second shaking mode or the third shaking mode depending upon whether the immediately preceding step was step  210 ,  214  or  216 , respectively. In other words, controller  110  will activate the implement cylinders  18  to curl the implement for the duration of the curl time, then de-activate the curl and activate movement in the dump direction for the duration of the dump time. When the dump time period has expired, the dump is deactivated and the curl repeats. This curl-dump cycle repeats for as long as the operator of the work vehicle engages shaker mode activation switch  80 . When the operator disengages switch  80 , the method moves to step  220 , which is returning to the first operational mode, being the condition of the shaking mechanism in steps  200  and  204 . 
     It is noted that when the shaking mechanism is operating in the first shaking mode, the implement  16  shakes about some neutral position, there being no net rotation or drift of the implement. When operating in the second shaking mode, the shaking mechanism tends to produce a net rotation of implement  16  in the dump direction. Likewise, when operating in the third shaking mode, the shaking mechanism tends to produce a net rotation of implement  16  in the curl direction. One specific advantage of the second shaking mode is that it dumps as it shakes, thereby efficiently enhancing removal of any residual sticky material from implement  16 . 
     Although the method of controlling the shaking mechanism has been described using the right hand manual control  65 , the method can be practiced when the foot pedal manual controls  55  are enabled and the hand manual controls  65  are disabled. In this case, controller  110  receives and uses signals from the right foot pedal stick implement control and position sensor  126  to determine if the right foot pedal manual control  55  is in the neutral position (step  208 ). When this condition is present, the method moves to step  210  and the shaking mechanism is directed by the remaining steps in the method to operate in the first shaking mode. Likewise, controller  110  can use the signals from the right foot pedal control and position sensor  126  to determiner if the right foot pedal manual control  55  is displaced in a right-ward displacement from the neutral position, thereby activating the second shaking mode of step  214 , or is displaced in a left-ward displacement from the neutral position, thereby activating the third shaking mode of step  216 . Thus, the method of controlling the shaking mechanism proceeds in a like manner as described above when the hand manual controls  65  are enabled with the foot pedal manual controls  55  disabled as it does when the foot pedal manual controls  55  are enabled with the hand manual controls  65  disabled. 
     While the present invention has been described with reference to certain preferred embodiments, one of ordinary skill in the art will recognize that additions, deletions, substitutions, modifications and improvements can be made while remaining within the spirit and scope of the present invention as defined by the appended claims.