Patent Publication Number: US-10309427-B2

Title: Variable pressure control system for dual acting actuators

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of U.S. application Ser. No. 15/049168, filed Feb. 22, 2016; which is a continuation of U.S. application Ser. No. 14/047,465, filed Oct. 7, 2013, now U.S. Pat. No. 9,301,438; which is a continuation of U.S. application Ser. No. 12/970,708, filed Dec. 16, 2010, now U.S. Pat. No. 8,550,020. 
    
    
     BACKGROUND 
     Most control systems for dual acting hydraulic or pneumatic cylinders or actuators utilize a directional control valve for controlling the flow of fluid under a constant or predefined pressure to force the actuator rod to extend or retract. In some applications, it would be desirable to not only control the direction of the fluid flow for actuating an actuator, but also to vary or regulate the fluid pressure in the fluid circuits for actuating the actuators. 
     One application in particular where it would be desirable to control the actuators as well as regulate or vary the fluid pressure in the fluid circuits is in connection with row cleaners on an agricultural planter. Row cleaners, such as disclosed in U.S. Pat. No. 7,673,570 (“the &#39;570 patent”), incorporated herein in its entirety by reference, are used to clear away crop residue, soil clods and other debris that can interfere with proper furrow formation and seed growth. When planting fields with heavy crop residue, it may be desirable to exert extra downforce on the row cleaner to ensure a more aggressive action of the row cleaner to clear away the heavy crop residue. In field conditions where the crop residue is light, a less aggressive action of the row cleaner may be desired. To increase or decrease the aggressiveness of the row cleaner while on-the-go during planting operations, a hydraulic or pneumatic cylinder is typically employed to raise and lower the row cleaner. In conventional control systems for raising and lowering row cleaners equipped with a hydraulic or pneumatic actuators, the operator&#39;s only control over the row cleaners is through movement of a lever fore or aft to open and close a directional control valve in the fluid circuit thereby causing the row cleaner actuator to extend or retract to respectively lower or raise the row cleaner. Accordingly, as the planter traverses the field, the operator is required to continually look back at the row cleaners and adjust their height up or down to maintain the desired amount of aggressiveness as the soil conditions, terrain and amount of crop residue vary. 
     The control system disclosed in the &#39;570 patent allows the operator to set a desired downpressure for the row cleaner which is then automatically maintained as the planter traverses the field. The &#39;570 patent also allows the operator to change the pressure of the hydraulic fluid supplied to the cylinders. However, the pressure in the fluid circuits is controlled through an electronic control system in combination with an accumulator having a hydraulic fluid chamber and a pressurized gas chamber. Thus, while the control system of the &#39;570 patent may serve its intended purpose it is a complex system with a higher associated cost. 
     It is desirable, therefore, to provide a control system which allows an operator to set a desired pressure in the fluid circuits so that as soil conditions and terrain vary during planting operations as the planter traverses the field, the actuator will self adjust to maintain the desired preset pressure in the fluid circuits. By maintaining the desired preset pressure in the fluid circuits, the row cleaner will follow the terrain or contours of the field while maintaining the desired amount of aggressiveness of the row cleaner. Furthermore, it would be desirable for such a control system to be relatively low in cost and simple to install and which is simple and intuitive to operate without the need for electronics and microprocessors. 
     Such a control system may have applications to other ground engaging devices on agricultural equipment or wherever there is a need for a low cost, simple and intuitive control system for providing directional control of hydraulic or pneumatic actuators over a range of variable pressures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a preferred embodiment of a control system for controlling fluid flow for actuation of one or more dual acting actuators. 
         FIG. 2A  is a front perspective view of a preferred embodiment of a controller for the control system of  FIG. 1 . 
         FIG. 2B  is a rear perspective view of the controller of  FIG. 2A . 
         FIG. 3A  is a perspective view of a preferred embodiment of a regulator assembly for the control system of  FIG. 1 . 
         FIG. 3B  is another perspective view of the regulator assembly of  FIG. 3A . 
         FIG. 3C  is another perspective view of the regulator assembly of  FIG. 3A . 
         FIG. 4  is a cross-sectional view of the regulator assembly as viewed along lines  4 - 4  of  FIG. 3A . 
         FIG. 5  is an exploded perspective view of a pressure regulating valve for the control system of  FIG. 1 . 
         FIG. 6  is a schematic illustration of the first and second fluid circuits of the control system of  FIG. 1 . 
         FIG. 7A  is a perspective view of a preferred embodiment of a piston for the regulator assembly of  FIG. 3A . 
         FIG. 7B  is a top plan view of the piston of  FIG. 7A . 
         FIG. 8A  is a perspective view of a preferred embodiment of a cam shaft for the regulator assembly of  FIG. 3A . 
         FIG. 8B  is another perspective view of the cam shaft of  FIG. 8A . 
         FIG. 8C  is a side elevation view of the cam shaft of  FIG. 8A . 
         FIG. 8D  is another perspective view of the cam shaft of  FIG. 8A . 
         FIG. 8E  is an end elevation view the cam shaft of  FIG. 8A . 
         FIG. 9  graphically illustrates the relationship of the fluid pressures in the down circuit and lift circuit versus the angular position of the user interface of the controller of  FIG. 2A . 
         FIG. 10  is a partial side elevation view of a row unit of an agricultural planter showing a row cleaner incorporating the control system of  FIG. 1 . 
         FIG. 11  is a perspective view of the row cleaner of  FIG. 10  incorporating the control system of  FIG. 1 . 
         FIG. 12  illustrates an alternative embodiment of a regulator biasing mechanism for the controller. 
     
    
    
     DESCRIPTION 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views,  FIG. 1  schematically illustrates a control system  100  for controlling actuation of one or more dual acting actuators  200 , such as pneumatic or hydraulic cylinders. The control system  100  includes a controller  300  and a pressure source  600 , which provides a substantially constant pressure to the controller  300 . Conduits  500  fluidly connect the pressure source  600 , the controller  300  and the actuators  200 . The controller  300  incorporates a pressure regulator assembly  400  which permits the operator to vary or regulate the pressure applied to actuate the actuators  200 . 
     As discussed later, the control system  100  is particularly adapted for use with an agricultural planter  10  ( FIG. 10 ) for controlling row cleaners  12  or other soil engaging members. However, those skilled in the art will appreciate that the control system  100  may have other equally suitable uses wherever it is desirable to provide a simple and intuitive means for directional control of hydraulic or pneumatic actuators over a range of variable fluid pressures. 
     It should also be appreciated that although the preferred embodiment of the control system  100  as described herein is a pneumatic system, those skilled in the art would understand the control system  100  could be adapted to a hydraulic system. Accordingly, the term “fluid” should be understood to include or refer to any fluid medium, including air, hydraulic oil or any other suitable fluid. Additionally, although the term “air” may be used when referring to the fluid used in the preferred embodiment or when describing a feature of the preferred embodiment, it should be understood that if the system  100  is adapted to a hydraulic system, any reference to air flow would of course be replaced with hydraulic oil or other fluid medium. 
     Referring to  FIGS. 2A and 2B , the controller  300  includes a pressure regulator assembly  400  ( FIG. 2B ). The pressure regulator assembly  400  is housed within the housing  302  of the controller. A user interface  304  is provided for interfacing with the pressure regulator assembly  400  and is preferably configured to be easily grasped by the hand of an operator such as a lever, a dial or the like. The controller  300  also preferably includes visual indicators that display the source pressure  306 , the lift pressure  308  and the down pressure  310 . The down pressure  310  is the amount of pressure on the side of the fluid circuit for extending the actuator ram  202  (hereinafter the “down circuit”). The lift pressure  308  is the amount of pressure on the side of the circuit for retracting the actuator ram  202  (hereinafter the “lift circuit”). The visual indicators  306 ,  308 ,  310  may be analog gauges or digital displays, or any other desired visual indicator of pressure in the respective fluid circuits. 
     By moving the user interface  304  (hereinafter the “lever  304 ”), the operator is preferably able to set the desired amount of fluid pressure in the down circuit and lift circuit by rotating the lever  304  clockwise or counter-clockwise as viewed in  FIG. 2A . The further the operator rotates the lever  304  counterclockwise or in the direction labeled “LIFT”, the greater the pressure in the lift circuit. Likewise, the further the operator rotates the lever  304  clockwise or in the direction labeled “DOWN,” the greater the pressure in the down circuit. As depicted in the embodiment of the controller  300  of  FIG. 2A , the pressure in the down circuits and lift circuits is variable over a range from 0 psi when the lever  304  is in the vertical position to 120 psi when the handle is rotated 90 degrees counterclockwise or 90 degrees clockwise.  FIG. 9  graphically illustrates how the pressure increases depending on the angular position of the lever  304  in either direction from the vertical neutral position at which point the pressure is zero and/or substantially equal or constant in both the down circuits and lift circuits. Of course, it should be appreciated that the pressure ranges, the user interface  304 , the visual indicators  306 ,  308 ,  310  and other features of the controller  300  described above may be altered or varied depending on preferences and the particular application of the control system  100 . As such, the controller  300  should not be construed as being limited to the particular embodiment described and illustrated herein. 
     A preferred embodiment of the pressure regulator assembly  400  is illustrated in  FIGS. 3A-3C .  FIG. 4  shows a cross-section of the preferred assembly  400  as viewed along lines  4 - 4  of  FIG. 3A . The pressure regulator assembly  400  includes a main body  402 , a first regulator  404 , a second regulator  406  and a regulator biasing mechanism  408 . The regulator biasing mechanism  408  is moveable within the main body  402  and cooperates with the first and second regulators  404 ,  406  for controlling the flow of air or other fluid therethrough as described in detail later. The regulator biasing mechanism  408  is operably connected to the user interface  304 , via a camshaft  470  (discussed later) such that movement of the user interface  304  results in a corresponding movement of the regulator biasing mechanism  408  within the main body  402 . 
       FIG. 5  is an exploded perspective view of the preferred first and second regulators  404 ,  406 . The first and second regulators  404 ,  406  are preferably ported regulators such as those manufactured by Norgren, Inc., model no. R07-100-RNLA, although other regulators having different configurations may be equally suitable. Each of the regulators  404 ,  406  comprises a regulator housing  410  defining an inlet port  412 , an outlet port  414  and a valve seat  416 . The inlet and outlet ports  412 ,  414  are preferably disposed at 90 degree angles from one another. A pressure regulating valve  420  is positioned within the valve seat  416  to control air flow from the inlet port  412  to the outlet port  414 . For clarity the inlet and outlet ports of the first regulator  404  are hereinafter referred to using reference characters  412 - 1  and  414 - 1 , respectively. Likewise, the inlet and outlet ports of the second regulator  406  are hereinafter referred to using reference characters  412 - 2  and  414 - 2 , respectively. 
       FIG. 6  schematically illustrates the preferred lift circuits and down circuits of the control system  100  for controlling the dual acting actuator  200 . The pressure supply  600  is in fluid communication with the tank pressure visual indicator  306  and the fluid inlet ports  412  of both the first and second regulators  404 ,  406 . The pressure regulating valve  420  regulates the fluid flow based on the position of the regulator biasing mechanism  408  controlled by the lever  304 . The first regulator outlet port  414 - 1  is in fluid communication with the lift circuit and visual indicator  308 . The second regulator outlet port  414 - 2  is in fluid communication with the down circuit and visual indicator  310 . 
     Referring again to  FIG. 4  in conjunction with  FIG. 5 , the pressure regulating valve  420  of the first and second regulators  404 ,  406  includes a diaphragm  422  and a valve body  424 . The valve body  424  has a cylindrical shaft  425 , an outer flange  426 , an axial opening  432  and axial fluid passageways  433 . The cylindrical shaft  425  of the valve body  426  is received within an o-ring  428 . The o-ring  428  is seated in the end of the valve seat  416 . The outer flange  426  rests on top of the o-ring  428 . The diaphragm stem  430  extends through the axial opening  432  in the valve body  424 . The valve spring  434  is received within the valve seat  416  and biases the plug  436  against the bottom end of the valve body  424 . 
     The regulators  404 ,  406  are preferably coaxially mounted to the ends of the main body  402  by a threaded connection. As the regulators are threaded into the ends of the main body  402 , a slip ring  438  and the peripheral edge of the diaphragm  422  are sandwiched between the end of the regulator housing  410  and an inside lip  440  of the main body  402  thereby creating a fluid tight seal. 
     Continuing to refer to  FIG. 4 , the main body  402  of the regulator assembly  400  includes an axial through-bore  450 . First and second sleeve bearings  452 ,  454  are preferably press fit into the through-bore  450 . First and second pistons  456 ,  458  are slidably received within the sleeve bearings  452 ,  454 , respectively. Each piston  456 ,  458  includes an axial partial-bore  460  at one end. As best illustrated in  FIG. 7 , the other end of each piston  456 ,  458  includes an arcuate face  462  ( FIG. 7B ) and a notch  464 . Seated within each partial-bore  460  of the first and second pistons are first and second piston springs  466 ,  468 . The other end of each of the first and second springs  466 ,  468  abuts the diaphragms  422  of the first and second regulators  404 ,  406  respectively. 
     Continuing to refer to  FIG. 4  in conjunction with  FIGS. 8A-8E , a camshaft  470  extends transversely through and is rotatably supported by the main body  402 . One end  476  of the camshaft  470  is preferably adapted for securing the lever  304  or other suitable user interface thereto. The other end of the camshaft  470  is preferably rotateably secured to the main body  402  by threading a nut  472  onto the threaded end of the camshaft  470 . Washers  471 ,  473  are preferably disposed between the nut  472  and the exterior of the main body  402 . At least one of the washers  471 ,  473  is preferably made of leather or other suitable material having a relatively high coefficient of friction such that when the nut  472  is sufficiently tightened against the washers, some frictional resistance against unwanted rotation of the lever  304  and camshaft  470  is achieved while still allowing the camshaft  470  to easily rotate. This frictional resistance allows the lever  304  to be moved to a desired position where it will remain in place until it is again grasped by the operator and moved to a new desired position. 
     The camshaft  470  further includes a stop plate  474  and first and second offset cams  480 ,  482 . As best illustrated in  FIG. 8E , each cam  480 ,  482  has a lobe  484  extending radially from the axis of the camshaft  470 . The lobes  484  of each cam  480 ,  482  are preferably angularly offset from one another by an angle W, which, in the preferred embodiment, is 38.6 degrees. The camshaft  470  further includes a guide disk  486 . As best illustrated in  FIG. 4 , the guide disk  486  is received within the notch  464  of the first and second pistons  456 ,  458 , to keep the pistons from rotating within the through-bore  450  of the main body  402 . 
     It should be appreciated that the first and second piston springs  466 ,  468  bias the first and second pistons  456 ,  458  axially inward toward the camshaft  470 . As the operator rotates the camshaft  470  by moving the lever or other user interface  304  from side-to-side, the lobes  484  of the first and second offset cams  480 ,  482  respectively rotate against the arcuate contact surfaces  462  of the first and second pistons  456 ,  458  forcing the pistons to move in the direction toward the respective regulators. The stop plate  474  on the camshaft  470  is oriented with respect to the cams  480 ,  482  such that the first and second edges  486 ,  488  of the stop plate  474  abut the stop screw  490  before the cams rotate beyond the center axis of the first and second pistons  456 ,  458 . 
     As previously described, in the preferred embodiment, the lever  304  is oriented in the vertical direction as shown in  FIG. 2  when the camshaft  470  is in the neutral position. In the vertical neutral position, the cams  480 ,  482  do not displace the pistons  456 ,  458  and the pressure regulating valves  420  are closed such that no fluid flows through the first or second outlet ports  414 - 1  or  414 - 2 , respectively and therefore the pressures in the down and lift circuits are substantially equal or constant. If the operator rotates the lever  304  clockwise as shown in  FIG. 2A  or to the left as viewed with respect to  FIG. 4 , the camshaft  470  to which the lever  304  is attached will likewise rotate clockwise causing the first cam  480  to rotate toward the first piston  456 . As the lobe  484  of the first cam  480  comes into contact with the arcuate face  462  of the first piston  456 , the first piston is forced axially leftward toward the first regulator  404 . The pressure regulating valve  420  remains closed until the axial position of the first piston  456  compresses the piston spring  466  enough to create a force sufficient to overcome any opposing bias of the valve spring  432  and resistance of the diaphragm  422 , at which point the diaphragm  422  will deflect to the left. When the diaphragm is deflected, the diaphragm stem  430  forces the valve plug  434  leftward, opening the axial passageways  433  ( FIG. 5 ) through the valve body  424  thereby allowing pressurized air from the pressure source  600  to flow through the valve body  424 , into the cavity  491  ( FIG. 4 ) and out through the first regulator outlet port  414 - 1 . Continued rotation of the lever  304  and camshaft  470  will cause the first piston  456  to continue to move axially to the left resulting in an increase in pressure in the down circuit as displayed on the “DOWN” visual indicator  310 . When the pressure in the down circuit increases sufficiently such that the pressure in the cavity  491  on the backside of the diaphragm  422  overcomes the biasing force of the piston spring  466 , the diaphragm  422  will return to its neutral or non-deflected state. The pressure in the down circuit will remain at this pressure until the lever  304  is moved further to the left or until the lever  304  is returned to the neutral position. 
     During planting operations, the operator will rotate the lever  304  to a desired down pressure position as indicated on the visual indicator  310  to achieve the desired aggressiveness of the row cleaner. If soil conditions change causing the row cleaner to pivot upwardly, the pressure in the down circuit will suddenly increase as the piston rod is forced inwardly. If the increase in pressure in the cavity  491  acting on the backside of the diaphragm  422  exceeds the bias of the piston spring  466 , the diaphragm will deflect to the right. As the diaphragm  422  and diaphragm stem  430  move to the right, the passageways  433  through the valve body  424  will be opened as the diaphragm stem  430  lifts off the valve plug  436  thereby permitting air to bleed off by passing through the axial passageway  492  extending through the diaphragm stem  430  and diaphragm  422 . The air will then pass into the through-bore  450  which is open to atmosphere by apertures  494  through the main body  402 . The air will continue to bleed off until the pressure on the backside of the diaphragm  422  in the cavity  491  is less than the bias of the piston spring  466  such that the diaphragm returns to its neutral or non-deflected state. With the diaphragm  422  in the neutral or non-deflected state, the passageways  433  are again closed off as the valve plug  436  abuts the end of the diaphragm stem  430 . The same action will occur if the operator rotates the lever  304  back to the center or neutral position from a down position. 
     Likewise if the soil conditions change causing the row cleaner to pivot downwardly, the pressure in the down circuit will suddenly decrease as the piston rod extends due to the loss of upward force exerted by the soil. If the pressure in the cavity  491  acting on the backside of the diaphragm  422  is less than the bias of the piston spring  466 , the diaphragm will deflect to the left. As the diaphragm  422  and diaphragm stem  430  move to the left, the passageways  433  through the valve body  424  will be opened thereby allowing pressurized air from the pressure source  600  to flow through the valve body  424 , into the cavity  491  and out through the first regulator outlet port  414 - 1 . When the pressure in the down circuit increases sufficiently such that the pressure in the cavity  491  on the backside of the diaphragm  422  overcomes the biasing force of the piston spring  466 , the diaphragm  422  will return to its neutral or non-deflected state. 
     Thus, it should be appreciated that the desired preset pressure in the down circuit as set by the position of lever  304  will be maintained by the pressure regulating valve opening and closing as necessary as soil elevations or other soil conditions change, thereby maintaining the desired amount of aggressiveness of the row cleaner with the soil. 
     It should be appreciated that because the second cam  482  is sufficiently offset from the first cam  480 , the second regulator  406  remains closed and no fluid flows through the second regulator outlet port  414 - 2  throughout the full range of clockwise rotation of the lever  304  and leftward deflection of the first piston  456 . As such, the pressure in the lift circuit remains substantially constant. It should also be appreciated that rotating the lever  304  counterclockwise as viewed in  FIG. 2A  or to the right as viewed in  FIG. 4  will result in the same but opposite movement of the second piston  458  and corresponding movement of the components of the second regulator  406  to permit fluid flow through the second regulator outlet  414 - 2 . Likewise, the first regulator  404  remains closed such that no fluid flows through the first regulator outlet port  414 - 1  throughout the full range of counterclockwise rotation of the lever  304  and rightward deflection of the second piston  456 . As such, the pressure in the down circuit remains substantially constant. This relationship is graphically represented in  FIG. 9  which illustrates that the pressures at the outlet ports  414 - 1  and  414 - 2  of the first and second regulators  404 ,  406  is a function of the angle of rotation of the lever  304  with respect to the neutral position, designated as 0 on the x-axis. Thus, when the lever  304  is rotated clockwise as viewed in  FIG. 2A , the pressure at the outlet port  414 - 1  of the first regulator  404  increases proportionally until the maximum pressure is achieved when the lever is at +90 degrees, while the pressure at the outlet port  414 - 2  of the second regulator  406  remains at zero. Conversely, when the lever  304  is rotated counterclockwise as viewed in  FIG. 2A , the pressure at the outlet port  414 - 2  of the second regulator  406  increases proportionally until the maximum pressure is achieved when the lever is at −90 degrees, while the pressure at the outlet port  414 - 1  of the first regulator  404  remains at zero. 
     It should be appreciated that with changes in the configuration and shape of the camshaft  470 , the pressure characteristics illustrated in  FIG. 9  may be varied. For example, the curves may be shifted apart such that both pressures are zero for lever positions within, e.g., 5 degrees of the neutral position. Similarly, the curves may be shifted together such that neither pressure is zero at the same time. The range of rotation required to obtain maximum pressure at each outlet port  414  may also be varied, and may be substantially symmetrical (as illustrated in  FIG. 9 ) or may be asymmetrical such that a lesser range of rotation is required to obtain full pressure at, e.g., outlet port  414 - 1  than  414 - 2 . 
     In all orientations of the lever  304 , the visual indicators  306 ,  308 ,  310  are configured to display the pressure at the pressure supply  600 , in the down circuit at the first regulator outlet  414 - 1 , and in the lift circuit at the second regulator outlet  414 - 2  respectively. And, as displayed in  FIG. 2 , it is preferred that the controller  300  is oriented such that when the operator turns or rotates the user interface  304  clockwise, the pressure in the down circuit increases. Likewise, when the operator turns or rotates the user interface  304  counterclockwise, the pressure in the lift circuit increases. In this manner, the control system  100  is intuitive to the operator. 
     Referring now to  FIGS. 10 and 11 , the control system  100  is illustrated in connection with a row cleaner  12  attached to a row unit  10  of an agricultural planter. Row units  10  such as described in U.S. Patent No. 4,009,668, incorporated herein in its entirety by reference, are well known in the art. Similarly, row cleaners  12  such as disclosed in U.S. Pat. No. 7,673,570 previously incorporated herein by reference, are well known in the art. The row cleaner  12  includes forwardly extending pivotal arms  14  to which ground engaging row cleaner wheels  16  are rotatably secured. The rearward ends of the row cleaner arms  14  are mounted to the row unit shank  20  by pins  22  forwardly of the furrow opening assembly  30  such that the arms  14  are free to pivot upwardly and downwardly relative to the soil surface. The row cleaner wheels  16  engage the soil surface and as the planter is drawn forwardly through the field as indicated by arrow  32 , the row cleaner wheels  16  rotate. As the wheels  16  rotate through the soil, their angled orientation with respect to the forward direction of the planter throws the debris to either side leaving a strip of soil substantially clear of debris in front of the furrow opening assembly  30 . 
     A bracket  710  is mounted to the row unit shank  20  by bolts or other suitable fastening means. The bracket  710  includes forwardly projecting ears  712 . A pin  714  pivotally secures one end of the actuator  200  to the ears  712 . The other end of the actuator  200  is pivotally secured to a plate  716  mounted to the forwardly extending row cleaner arms  14 . Air hoses or conduits  500  fluidly connect the actuator  200  to the controller  300  and to the respective first and second regulator outlet ports  414 - 1 ,  414 - 2  as previously described. The controller  300  (not shown in  FIGS. 10 and 11 ) is preferably mounted within the cab of the tractor for controlling and viewing by the operator. The pressure source  600  (not shown in  FIGS. 10 and 11 ) is preferably mounted to the planter frame. A preferred pressure source  600  suitable for controlling row cleaners on a planter as hereinafter described is a 2 gallon, 12 volt air compressor, such as the air compressor available from VIAIR, model no. 350c, in Irvine Calif. 
     It should be appreciated that the mass of the row cleaner  12  alone will impose a downward force on the soil surface as the planter traverses the field. However, by incorporating the control system  100  as described above, the operator is able to increase the downward force by rotating the lever  304  counterclockwise in the direction of the visual indicator  310  preferably labeled “DOWN” as shown in  FIG. 2A . As previously described, rotating the lever  304  will result in an increase in the fluid pressure in the down circuit forcing the actuator rod  202  ( FIG. 6 ) to extend forcing the row cleaner to pivot downwardly into further engagement with the soil causing more aggressive action of the row cleaner wheels  16 . Likewise, to lift the row cleaners  12  so that the row cleaner wheels  16  are raised above the soil surface (for example when turning the planter at the headlands) or when less aggressive action of the row cleaner wheels is desired (for example when debris is light or other changes in soil conditions) the operator may rotate the lever  304  clockwise in the direction of the visual indicator  308  preferably labeled “LIFT” as shown in  FIG. 2A . To fully lift the row cleaner  12  so that the row cleaner wheels  16  are raised above the soil surface, the lever  304  is turned clockwise far enough to the “LIFT” side to provide sufficient pressure in the lift circuit such that the actuator rod  202  ( FIG. 6 ) retracts far enough to rotate the row unit arms  14  about the pin  22  until the row cleaner wheels  16  are above the soil surface. 
     As illustrated in  FIG. 1 , the controller  300  may control multiple actuators  200  and thus multiple row cleaners  12 . Alternatively, multiple controllers  300  may be employed to control individual actuators and row units or groups of actuators and row units. 
     In addition, it should be appreciated that other implementations may be made of the control system  100  as described herein. For example, the control system  100  may be used to vary the downforce on other ground engaging components of a planter, such as a row unit downforce system as disclosed in U.S. Pat. No. 6,389,999 or Applicant&#39;s co-pending application Ser. No. 12/679,710 (Pub. No. 2010/0198529), both of which are incorporated herein in their entireties by reference, to vary the downforce imposed on a row unit of the planter by an actuator such as cylinders or air bags. The control system  100  may be adapted to provide variable pressure to the down and lift circuits associated with such downforce actuators, enabling a user to control the downforce on the row unit. As discussed above with respect to the row cleaners  12 , the control device may be adapted to simultaneously control the downforce on all of the row units. Alternatively, multiple control devices may be adapted to control sections or individual row units of the planter. 
     Similarly, in a planter such as that disclosed in U.S. Pat. No. 4,009,668, previously incorporated by reference above, the downforce on the closing wheels of the row unit are typically varied by an actuator such as a spring (indicated by reference numeral 59 in the &#39;668 patent). In one implementation, the actuator associated with each closing unit may be the actuator  200 . The pressures associated with the actuator  200  may be controlled by the control system  100  as disclosed herein. Thus, the user is able to vary the downforce on the closing wheels of the row unit from the cab. As discussed above with respect to the downforce actuator, such a system may be adapted to control all of the closing wheels across the entire planter or individual closing wheels or groups of closing wheels. 
     Those skilled in the art will also appreciate that various configurations of the camshaft  470  and the lobes  484  and the orientations of the cams  480 ,  482  may be suitable. Additionally, rather than cams, the camshaft  470  may utilize a worm gear or other suitable cooperating arrangements to convert rotation of the camshaft into linear or axial movement of the pistons. 
     Moreover, in other embodiments, the cams  480 ,  482  may be modified such that a constant force is applied to one of the piston springs  466 ,  468  while the force on the other piston spring is varied. In such embodiments, as the user varies the pressure at one circuit output, the pressure at the other circuit output remains at a constant non-zero value. 
     In still other embodiments, the cams  480 ,  482  may be modified such that a varying force is applied to one piston spring  466 ,  468  while the force on the other piston spring is varied. For example, the cams  480 ,  482  could be configured such that as the user moves the lever  304  from a first orientation to a second orientation, the pressure in the first circuit steadily increases and the pressure in the second circuit steadily decreases. 
     Moreover, further embodiments of the regulator assembly  400  may be made to control the fluid pressures in more than two circuits. For example, a second main body  402  may be provided with a second set of pistons may be provided with a longer camshaft  470  incorporating a second set of cams extending through both main bodies. Thus, as the operator turns the lever  304 , multiple regulators may be opened or closed to control fluid flow through multiple circuits. 
     In still other embodiments, the controller  400  may be modified to provide an alternative regulator biasing mechanism  408  such that camshaft  470  is replaced with other devices configured to alternately displace the pistons  456 ,  458  upon rotation of the lever  304 . For example, as illustrated in  FIG. 12  the regulator biasing mechanism  408  may comprise a rack and pinion arrangement. In this embodiment, the rack  802  is slidably mounted within the main body  402  such that it is constrained to rotate in a leftward or rightward direction from the perspective shown in  FIG. 12 . The pinion  804  is mounted to the lever  304  such that when the operator turns the lever  304  the rack  802  contacts one of the pistons  456 ,  458 . The dimensions and gearing of the rack and pinion are preferably such that a user can move one of the pistons  456 ,  458  through the desired range of motion, thus providing the desired range of pressures at the associated outlet ports  414 - 1 ,  414 - 2  of the first and second regulators  404 ,  406 , respectively, while the other piston remains unmoved. 
     The foregoing description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiment of the apparatus, and the general principles and features of the system and methods described herein will be readily apparent to those of skill in the art. Thus, the present invention is not to be limited to the embodiments of the apparatus, system and methods described above and illustrated in the drawing figures, but is to be accorded the widest scope consistent with the spirit and scope of the appended claims.