Abstract:
An agricultural implement, having ground engaging tools mounted on subframes that are movable through hydraulic actuators between raised transport and lowered working positions, is provided with a hydraulic circuit in which the actuators are connected in parallel with one another within a grouping of the actuators. The positioning of the ground engaging tools into a lowered working position closes the hydraulic circuit for the group of actuators. The subframes are arranged to float over ground undulations to maintain a common working depth for the ground engaging tools. The vertical movement of any one of the actuators in the common group will force a displacement of a corresponding amount of hydraulic fluid, which will then be shared by all of the remaining actuators in the corresponding group. A depth averaging control for the ground engaging tools and a mechanical headland stop apparatus are also provided for the agricultural implement.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims domestic priority on U.S. Provisional Patent Application Ser. No. 60/108,025, filed on Nov. 12, 1998, the contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to agricultural implements such as cultivators that have a framework for supporting ground engaging tools that can be used for a variety of farming operations including tilling soil, applying fertilizer, and seeding. Implements such as these can be effectively used in different farming practices such as conventional-till, low-till, or no-till methods. Such implements required a framework through which, during operation, draft forces are transmitted with a minimum of moment forces being generated, which otherwise force some ground engaging tools to work deeper while causing others to work more shallow than the desired set working depth. 
     It is also desirable and common for implements of this type to have hitch frames pivotally connected to the front of the implement for connection to a pulling, vehicle, providing up-down movement of the forward end of the hitch relative to the implement so the implement frame is better able to remain parallel to the ground being engaged. There have also been implements of these types which have a framework of wing sections that pivot relative to one another along axis aligned with a direction of travel so the individual sections are able to remain parallel to respective sectional regions of the ground being engaged. 
     Known tillage implements have wings or sections pivotal to each other on axis that are angled from a direction of travel, providing some accommodation for ground that varies in slope in which the pitch varies from the left to right side of the implement framework. Other implements show a framework which is loosely jointed such that it can twist to accommodate such variations in ground pitch. 
     These implements of the prior art have served well to provide good ground following a depth control for a variety of farming operations. But it is yet desirable to provide an implement that has excellent ground following characteristics, yet also is capable of very compact folding. As farms become larger, implements are transported greater distances between fields. Implements of larger widths are being used to perform farming operations in reduced time. It is desirable to provide an implement that is available in large widths, is easily configurable for transport on roadways in which the implement is folded compactly having small dimensions in width and height for transport. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide an implement with good ground following ability for consistent depth control across the whole implement, the implement being able to conform to variation in both ground pitch and roll. 
     It is also an object of this invention to provide an implement frame having such ground following characteristics which can be folded compactly for low and narrow transport. 
     It is also an object of this invention to provide an implement which is modular and capable of being configured when assembled for attachment of hoe or disc type ground engaging tools, and be used for either conventional-till, low-till, or no-till operations. 
     It is a further object of this invention to provide a framework through which biasing forces can be applied to transfer downward forces to distal ends of the framework. 
     These and other objects, features, and advantage are accomplished by the present invention by providing an agricultural implement, having ground engaging tools mounted on subframes that are movable through hydraulic actuators between raised transport and lowered working positions, with a hydraulic circuit in which the actuators are connected in parallel with one another within a grouping of the actuators. The positioning of the ground engaging tools into a lowered working position closes the hydraulic circuit for the group of actuators. The subframes are arranged to float over ground undulations to maintain a common working depth for the ground engaging tools. The vertical movement of any one of the actuators in the common group will force a displacement of a corresponding amount of hydraulic fluid, which will then be shared by all of the remaining actuators in the corresponding group. A depth averaging control for the ground engaging tools and a mechanical headland stop apparatus are also provided for the agricultural implement. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The advantages of this invention will be apparent upon consideration of the following detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings wherein: 
     FIG. 1 is a perspective view of a schematic diagram of a modular implement having a 5 section drawbar with subframes attached to each section of the drawbar, and is shown in a field working position; 
     FIG. 2 is a perspective view of the implement in FIG. 1 shown in a raised non-working position; 
     FIG. 3 is a perspective view of the implement in FIG. 1 shown with the drawbar fully rotated and raised to an intermediate position; 
     FIG. 4 is a perspective view showing subframes rotated to a generally vertical transport position; 
     FIG. 5 is another perspective view of the implement in FIG. 1 showing one of the wing sections of the drawbar folded rearwardly to a compact transport position; 
     FIG. 6 is a schematic side view of the implement in FIG. 1 shown in a working position, the ground engaging tools not being shown for purposes of clarity; 
     FIG. 7 is a schematic side view of the implement in FIG. 6 shown to be raised to a headland position; 
     FIG. 8 is a schematic side view of the implement in FIG. 6 shown with the drawbar fully rotated to the intermediate position as in FIG. 3; 
     FIG. 9 is a schematic side view of a center subframe of the implement in FIG. 1, shown in a working position; 
     FIG. 10 is a schematic side view of the center subframe in FIG. 9, shown with the drawbar being rotatably raised to a headland position such as in FIG. 7; 
     FIG. 11 is a schematic side view of the center subframe shown in FIG. 9, shown in a low position with the drawbar being fully rotated and raised to the intermediate position as in FIG. 3; 
     FIG. 12 is a schematic side view of the implement in FIG. 1, showing wing subframes having been raised to a transport position and showing the center subframe remaining in a low position; 
     FIG. 13 is a schematic plan view of the implement in FIG. 1, shown in a working position; 
     FIG. 14 is a schematic plan view of the implement in FIG. 1, shown in the intermediate position; 
     FIG. 15 is a detail view of the hitch frame showing a locking mechanism for locking the drawbar to the hitch frame, restricting it from downward rotation; 
     FIG. 16 is an illustration of a modular implement like that shown in FIG. 1, but having only 3 drawbar sections, and showing the detail of a wing wheel assembly with its respective wheel position actuator, the drawbar being shown in a deep working position; 
     FIG. 17 is a illustration of the implement in FIG. 16 shown with the drawbar rotated to a shallow working position; 
     FIG. 18 is a detailed illustration of a wing wheel assembly caster locking mechanism and wheel position actuator, showing the locking mechanism unlocked, and the wheel assembly actuated to a field position; 
     FIG. 19 is the wheel assembly in FIG. 18 shown to be actuated to a transport position and the locking mechanism in the locked position, restricting the caster action of the wheel assembly; 
     FIG. 20 a hydraulic schematic showing a depth control hydraulic circuit with a depth averaging link illustrated and superimposed on the schematic; 
     FIG. 21 is a detail illustration of the depth averaging linkage attached to a drawbar wing section of a modular implement such as the one shown in FIG. 1; and 
     FIG. 22 is a comprehensive hydraulic schematic showing both the wing fold circuit and the subframe actuator circuit with mechanical links superimposed onto the schematic to illustrate a headland position control and other automatic control features. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A modular assembly of one configuration of an implement according to the invention is shown in plan view in FIG.  13 . It is shown schematically in FIGS. 1-5, and side views of various positions of the implement are shown in FIGS. 6-12. It is shown having a hitch section  21  with a tongue  23  for connection to a pulling vehicle (not shown). The hitch section is supported on a set of ground wheel assemblies  1 , which the support the hitch section  21  to roll above the ground as it is pulled in an operating or transport direction  22 . Further direction references made within this description are made in relation to the operational direction  22 . A drawbar  20  is pivotally attached to the hitch section  21  on a transverse pivot axis  24 , at joints  24   a  and  24   b.  Subframes  27  and  28  are pivotally attached to the drawbar  20  and in a working position shown in FIG.  1  and FIG.  6 . The subframes extend rearwardly of the drawbar and are supported parallel to the ground surface. Wheel assemblies  29  and  31  are pivotally attached to the rearward end of the subframes  28  and  27  respectively, for supporting the pivotal subframes at a level above the ground. The wheel assemblies  29  and  31  are linked to the drawbar  20  for coordinating the pivotal movement and position of the wheel assemblies with that of the drawbar as the drawbar  20  is pivotally operated about axis  24 . Details of the coordination of these movements will be described in greater detail below. 
     The drawbar  20  extends laterally behind the hitch section  21  and is divided into sections with a center section attached to the hitch having a wing section attached to each lateral end of the center section. Wide models of the implement may have additional wing sections attached to each side, defining inner wing sections  20   b  and  20   d  and outer wing sections  20   a  and  20   e  of the drawbar on each side of the center section  20   c.  Each wing section is attached at a first end to an adjacent inner section an is supported by a wing wheel assembly  1 ′ at a point toward a distal second end of the wing section. The wing attachment provides pivotal movement of the wing section so that the distal end is allowed movement up or down relative to the inner end when the drawbar is in any of its positions ranging from a working position to a transport position. In a working position, the drawbar  20  is rotated rearward and downward to set the ground engaging tools at a ground engaging depth within the ground. In an intermediate position the drawbar is rotated fully upward in which the ground engaging tools are raised out of contact with the ground. In the transport position, the drawbar wing sections are pivotally folded to trail rearwardly of the center section  20   c,  as seen in FIG. 5 which shows wings on one side of the implement folded so. 
     FIG. 6 shows that a subframe  28  is attached to the drawbar  20  and is pivotal relative to the drawbar about an axis  30 . The pivotal movement of the subframe relative to the drawbar is controlled by an actuator  36  which is attached at one end  38  to the subframe and at another end  37  to the drawbar. As viewed in FIG. 6, retraction of the actuator will effect clockwise rotation of the subframe relative to the drawbar. A link  35  is connected at one end  39  to the drawbar and at another end  40  to the subframe wheel assembly  29 . When the subframe is rotated clockwise relative to the drawbar  20 , the link will allow the wheel assembly  29  to rotate clockwise relative to the subframe  28 . As the subframe is rotated clockwise relative to the drawbar, and the wheel assembly is thus also rotated clockwise, then the subframe  28  will be lowered toward the ground. The link is connected to the drawbar  20  and wheel assembly  29  such that the amount of rotation of the wheel assembly  29  relative to the rotation of the drawbar  20 , is such that the subframe  28  will be raised and lowered in a level manner through a working range of positions so that it is maintained parallel to the ground in such a range of positions. The rotation of the drawbar relative to the hitch remains free, so the hitch remains floating, as is common with many implements of this type. The portions of the frame supporting the ground working tools are supported by wheel assemblies  1 ,  1 ′,  29  and  31 , which are spaced close to each other in fore and aft relation so that the slope of the ground being engaged is closely followed by the framework of the implement which is supporting the ground engaging tools. 
     Optional actuators can be connected between the hitch section and the drawbar and used to bias the drawbar downward from the hitch section. This transfers the weight of the hitch section onto the drawbar so extra force is available to press the ground working tools into engagement with the ground to the desired set working depth. The subframes bear much of the weight of the drawbar when it is in the downward rotated position, the drawbar sections also being partially supported by wheel assemblies  1  and  1 ′ so the drawbar remains at a constant height and follows a slope of land which may roll up or down to the left or right of the center of the implement. Pivotal movement of the subframes relative to the drawbar also accommodate variations in pitch of the ground up or down fore and aft of the implement. This pitch may vary from the left to the right side of the implement. The subframes are able to accommodate such variation in a manner described in more detail below. 
     A subframe  27  is shown attached to the drawbar center section  20   c  shown in a working position in FIG.  9 . The forward end of the subframe  27  is supported in a slot  42 , the slot being a part of a plate like member attached to the drawbar, the plate member also having a journal for attaching the drawbar to the hitch at axis  24 . The detail of the plate member is shown in FIG.  15 . Two such plate members are spaced laterally on the drawbar center section  20   c  to either side of the center of the section as can be seen in FIG. 13. A track member is also attached to the drawbar center section which guides movement of the first end  41  of the wheel assembly link  35 . Link  44  is pivotally attached at one end to the hitch section and at the other end is pivotally attached to the subframe  27  at  30 . Link  42  is pivotally attached at one end to the hitch section  21  and at the other end is pivotally attached to the first end  41  of link  35 . As the drawbar is rotated, link  44  guides the movement of the subframe at point  30  along the slot  42 , while the link  44  guides the movement of the link end  41  along the track member. This maintains the center subframe in a low position when the drawbar is rotate fully up to the intermediate position. This provides clearance between the center subframe and ground engaging tools attached to the underside of the wing subframes when the drawbar wings are folded rearward to the transport position shown in FIG.  5 . 
     Modular Subframe Construction 
     The modular assembly of one configuration of an implement according to the invention is shown in plan view in FIG.  13 . This configuration is assembled with subframes that are adapted for attaching 2 rows of disc type ground engaging tools (not shown) on fore and aft transverse toolbars of each subframe. The subframes  28  and  27  are attached to a drawbar  20  and are attached laterally adjacent one another to extend transversely across a wide path on the ground. Subframes  28  which are to the right of the center of the drawbar are generally identical which has obvious manufacturing advantages, reducing cost of construction. Subframes  28  to the left of the center of the drawbar  20  are generally identical and symmetric to those on the right, also having cost reducing manufacturing advantages. A subframe  27  is attached to a drawbar center section  20   c.  This subframe is controlled differently from subframes  28  as has been described above. 
     An alternate subframe construction (not shown) is available for assembly with the drawbar, and when configured with such subframes, the implement is operable as a cultivator or hoe drill seeder. The alternate subframes can comprise of multiple transverse toollbars: 3, 4, or 5, as may be desirable for various arrangements of ground engaging tool supports (not shown) which can be attached to the toolbars as is common in cultivator construction. The alternate subframes of this configuration can be supported at the rearward ends by alternate wheel assemblies  29  and  31 , which can have a gang of press wheels attached at their first ends for rolling support of the subframe while also providing closing and packing of each of the furrows created by the ground engaging tools as the implement is pulled forward in operation. The press wheels are spaced so that there is one press wheel corresponding to each furrow created by the implement. 
     Parallel Actuator Hydraulic Circuit 
     As the implement is pulled across the ground, uneven slopes that roll and pitch may be encountered by the implement framework. The roll can be easily accommodated by jointed drawbar sections similar to that which is common on agricultural harrow implements and somewhat similar to conventional folding cultivators. Variations in pitch can also be accommodated by the present invention in a manner which is similar to that on agricultural harrow implements, the application of which was not before obvious as applied to cultivators and seeding implements which required the ground engaging depth of the ground engaging tools to be accurately controlled. The present invention provides rear wheel assemblies on each of the subframes of the implement so both the forward and rearward end of the subframes are controlled to a set height. The rear wheel assemblies of the present invention are pivotally attached, the movement of which is coordinated with the movement of the drawbar supporting the forward end of the subframes so that the subframes can be easily adjusted to various heights in a range of working positions in which the subframes are maintained parallel to the ground. 
     Actuators  36 , which control the movement of the drawbar and thereby the movement of the subframes, are connected in parallel for simultaneous operation of all the subframe actuators in a common circuit. The connection of the actuators to a common drawbar maintains their retraction and extension in a synchronized manner so the subframes move between various working positions in unison at remain at equal working heights. The subframes are provided independent movement relative to each other about the drawbar pivots  30  so that their frame heights remain equal regardless of variations in ground elevation and slope differences between the subframes from the left to right sides of the implement. When the implement is set at a working position, the circuit controlling the subframe actuators is closed, yet the subframe actuators are still able to communicate fluid between themselves to allow the subframes continued independent movement. 
     The center subframe  27  is not controlled by an actuator and is positionable by the rotation of the drawbar, the drawbar being controlled by the actuators  36  of the subframes  28 . 
     Depth Averaging Control 
     FIG. 22 schematically shows a depth control circuit  300  for controlling the depth of the ground engaging tools by controlling the movement of the subframe actuators  36 . When the subframes are lowered to a working position by retraction of the actuators  36 , the implement may not be positioned over level ground. Some subframes may pitch upward at the forward ends relative to others which may be pitched less upward, or even downward. 
     To lower the implement to a working height, hydraulic pressure is applied to circuit  300  in line  301 . This cause actuators  36  to retract, rotating the subframes clockwise relative to the drawbar and rotating the drawbar ccw and downward as viewed schematically in FIG.  22 . Fluid displaced from the base ends of actuators  36  during their retraction is returned to the hydraulic reservoir, not shown, via line  302 . Depth stop valves  303  are actuated when the level of the subframes has approached a set working height, and flow to line  302  is blocked restricting flow in or out of circuit  300 . Actuators  36  of the preferred embodiment are connected to the circuit  300  in two groups, the groups being separately controlled by individual depth stop controls  303 . The drawbar wing sections of the preferred implement are provided with rotational movement relative to the center section  20   e.  Thus the rotation of the drawbar wing sections to the left and right of the center section are controlled separately by the two depth control valves  303  as shown. As each wing section or sections to the left or right of the center section approach the set working position, the respective depth stop control is actuated stopping the drawbar rotation to a set position. 
     FIG. 21 illustrates a depth stop linkage which actuates the depth stop control valve  303 . An averaging link  304  is connected to adjacent subframes that are attached to a common drawbar wing section. One, two, or more subframes may be attached to each drawbar section. When two or more are attached it is desirable to use their average position for actuating a depth stop control, so that the drawbar section is set at an average height not effected by a severely pitched position of any one subframe, which may happen if the subframe is on pitched ground, or if the subframe wheel assembly  29  is resting on a clod or rock. A central part of the averaging link  304  abuts a depth control crank  305 . The crank  305  is rotated according to the relative rotation between the drawbar and adjacent subframes. The crank  305  is linked to a lever  307  by a linking member  306 . The lining member  306  may be directly connected to lever  307 , or for an implement having inner and outer wing sections, it can be indirectly linked to the lever  307  as shown in FIG.  21 . 
     A second pair of adjacent subframes (not shown) which are attached to an outer wing section, have an identical averaging link  304  acting on an identical crank  305 , to which a link  306  is also connected. Links  306  can be connected to an intermediate lever on one end of lever  307  for averaging the actuation of the links  306 , or as shown, link  306  can be a continuous cable with each end attached to cranks  305  with an intermediate portion of the cable looped around a pulley  308  for averaging the actuation of the cable from both ends by cranks  305 . This averaged cable displacement rotates lever  307 . A link  309  attached to the other end of the lever  307  is thereby operated in a linear manner. A depth stop  310  is adjustably positioned on the link  309 , and is setable to a position corresponding to a desired set working height of the implement framework. When the drawbar is lowered and the subframes pivot relative to the (drawbar to actuate the depth averaging link  320 , the depth stop  309  will actuate the stop valve  303 , stopping further rotation of the drawbar and holding the respective subframes at a set working height. 
     Headland Position 
     FIG. 22 also shows headland stop valve  330 . A linkage  331  attached to the drawbar  20  is shown schematically which actuates the headland stop valve  330 , when the drawbar reaches a certain position when being raised from a working position in which ground engaging tools are engaging the ground, to a position in which the ground engaging tools are raised out of contact with the ground. The headland link (not otherwise shown) includes a stop which is adjustable along the length of the link. The stop can be set to actuate the headland valve  330 , when the drawbar is raised to a position about  30  degrees up from the working position as shown in FIG.  7 . This is a position to which the implement is raised at field headlands to raise the ground engaging tools just enough to allow turning of the implement at headlands. This can be a position in which the ground engaging tools are out of contact with the ground, or in which the tools are in shallow contact with the ground, providing a sweeping action so no wheel tracks remain visible where the implement is turned. From this position the implement ground engaging tools can be more quickly set back to a working depth. 
     A bypass linkage (not shown) is connected a drawbar locking crank  50  which is visible in FIG.  15 . The lock crank  50  is operable from handle  52  and can be positioned to abut with lock  48  that is attached to the drawbar  20 , lifting it out of engagement with lock hook  47  that is attached to the hitch section  21 . When the crank  50  is rotated clockwise as viewed in FIG. 15, then the lock  48  is engagable with hook  47  when the drawbar becomes fully raised up. The bypass link (not shown) is also operated by crank  50  so that it shifts the alignment of headland link  331  (also not shown in FIG. 15) so that it does not engage the headland stop  330  as the drawbar is being raised up. In this way the drawbar can be fully raised up and not stopped at the headland position. 
     An alternate implement used for supporting precision row planting devices, is provided with a similar headland position stop. The mechanism of operation of the headland stop in this implement is different, but the general function is the same. The planting implement comprises a drawbar hitch for connection to a pulling vehicle, a transversely extending toolbar pivotally attached to the drawbar about a transverse axis for rotation between a downward working position and upward non-working positions, and having planting devices attached in spaced relation along the toolbar. The implement includes a hydraulic circuit with a toolbar actuator for rotating the toolbar between positions, and hydraulic valves for controlling the hydraulic circuit. 
     The implement also includes an electronic control system which is connected to solenoids that operate various hydraulic valves within the hydraulic circuit, and in particular, controls the operation of a toolbar actuator valve to allow or restrict hydraulic flow which operates the toolbar actuator. The headland stop control comprises a proximity sensor attached to the drawbar, the sensor being of the type which has electrical characteristics which change when a ferrous material is placed proximate to the sensor. The toolbar of the implement has attached to it a steel plate which works in cooperation with the proximity sensor. The position of the headland sensor is adjustable on the drawbar so that the position of the toolbar in which the steel plate becomes proximate to the sensor can be adjusted to vary the headland position. As the toolbar is being raised from a working position to a non-working position, the steel plate is rotated with the toolbar and becomes proximate to the headland sensor. This signals the electronic controls system to cause actuation of the toolbar hydraulic valve to stop the upward movement of the toolbar. 
     The electronic control system includes an override switch which, among other functions, interrupts the headland stop signal so that the toolbar may be raised to a fully upwardly rotated position. As for the headland stop position of the implement previously described, the headland stop control of this alternate implement stops the toolbar when it is being raised at headlands, at a position from which it can be more quickly be reset to a working position again than if it had to travel from a more upwardly raised position. 
     Unfold Circuit with Wheel Control in Combination 
     The implement shown in FIG. 13 includes wing wheel assemblies  1 ′ for supporting the drawbar wing sections as described above. The wing wheel assembly  1 ′ is shown in greater detail in FIG. 18. A wing wheel assembly is attached near the distal end of each wing section  20   a,    20   b,    20   d,  and  20   e.  The assembly has a main strut  6  which is attached to a wing drawbar section by a journal arrangement having a steering axis  10 . A lockable caster arm  5  is pivotally supported by the strut  6  and, when not locked, provides caster motion to the wheel assembly. Wheels  2  and  3  are pivotally supported on parallel axles having axes  2   a  and  3   a,  the axles being attached to a walking beam axle having walking axis  4 , with axes  2   a  and  3   a  being offset an equal distance from the walking axis  4 . 
     A lock member  14  is pivotally supported by a bolt running through journal  16  and is free to pivot by the force of gravity. The lock  4  is adapted to fit within a locking saddle  15  which is fixed to the strut  6 , and when engaged in the saddle  15 , prevents rotation of the caster arm  5  about axis  7 . The wing wheel assembly is pivotally controlled by a wheel steering actuator  11 , connected at one end  13  to the strut  6 , and at the other end to the drawbar wing. Extension and retraction of the wheel steering actuator  11  effects rotation of the wing wheel assembly  1 ′ about the steering axis  10 . The caster axis  7  is generally vertical when the drawbar  20  is rotated within a range of field positions, which is a range including a working position and a headland position, although it may be somewhat inclined forward or rearward. 
     The walking beam arrangement accommodates various positions of the caster axis while maintaining both wheels of the assembly on the ground so the height of the drawbar remains generally constant as the caster rotates and so that the load is evenly distributed. As the drawbar  20  is rotated upward to a transport position, the caster axis  7  becomes generally horizontal and lock  14  is pivoted by gravitational force to rest against saddle  5 . If it does not immediately engage in the saddle, then it will soon become engaged during folding of the drawbar wings or as transporting of the implement begins to restrict rotation about axis  7  and provide stability to the wheel assembly during transport. 
     The wing wheel assemblies  1 ′ of the drawbar wing sections are steered into alignment for either transport of field operation. The movement of a wing wheel assemblies  1 ′ is controlled by an actuator  11  which is connected to a common circuit wing fold circuit  400  in parallel hydraulic connection with wing fold actuators  403  (not shown) that are connected between the drawbar center section and inner wing section. The number of hydraulic circuits requiring connection to the pulling vehicle is thereby minimized by having such a combination circuit. The wing wheel actuator  11  operation is sequenced by a hydraulic valve  405  so the wheel assembly  1 ′ is steered at the appropriate moment during the folding and unfolding of the implement wing sections. 
     Folding Sequence 
     1. To configure the implement for transport from a field position, the subframes are raised and the drawbar wings are folded. The wing wheel assemblies are steered in sequence as the drawbar wings are folded. The sequence begins by first setting the drawbar lock handle  52  to a locking position so that locks  48  are ready to engage hooks  47 . This sets the headland link  331  to bypass the headland stop valve  330 . 
     2. Hydraulic pressure is then applied to line  302  to cause subframe actuators  36  to extend and fully rotate the drawbar  20  until it is locked with the hitch section  21 , restricting its rotation. 
     3. Hydraulic pressure is then applied to line  301  to cause subframe actuators  36  to retract. With the drawbar  20  locked, the subframes  28  are raised off the ground to a generally upright transport position as shown in FIG.  12  and FIG.  4 . 
     4. Now pressure is applied to line  401  of the hydraulic fold circuit  400 . This first causes a draft arm lock actuator  406  to retract to unlock draft arm locks, releasing draft arms which otherwise support the drawbar wing sections during field operation. After this is complete, the pressure increases to extend the wing fold actuators  403 , folding the drawbar wing sections rearwardly. 
     5. As a drawbar wing section is nearly completely folded to a transport position as shown in FIG. 5, then a wheel actuator link (not shown), being responsive to the drawbar wing rotation, actuates the wheel actuator sequence valve  405  to allow hydraulic fluid to flow from the base end of wheel actuator  11  to the hydraulic reservoir (not shown). The actuator  11  is then retracted and the wing wheel assembly  1 ′ is steered about 90 degrees about the now upright steering axis  10  to align the wheels in a direction suited for transport as the wings become completed folded back. 
     Unfolding Sequence 
     1. To unfold the implement to a field operating configuration the sequence is reversed. Pressure is first applied to line  402  to unfold the wings, but the pressure first causes the draft arm lock actuator  406  to extend and wheel actuators  11  to extend and the wing wheel assemblies  1 ′ to be steered about 90 degrees to align the wheels about perpendicular to the transport direction. The draft arm locks (not shown) are now ready to engage with the ends of draft arms  46  so they become locked with the hitch section  21 . They are spring biased to allow the locks some pivotal motion during engagement. When movement of the lock actuator  406  and wing wheel actuators  11  is complete, the pressure increases to cause the wing fold actuators  403  to retract and unfold the wings to a laterally aligned position. 
     2. Pressure is now applied to line  302  to cause subframe actuators  36  to extend and lower the subframes  28  to be generally parallel with the ground and so they are supported at their rearward ends by wheel assemblies  29  such that the weight of the drawbar is relieved from the locks  48  and the locks  48  can be disengaged from lock hooks  47 . 
     3. Pressure is now applied to line  301  to cause the subframe actuators  36  to retract, rotating the drawbar  20  downward to a field operating position. At this time the caster lock  14  will fall out of engagement with saddle  15  to allow the castering motion about the now generally vertical axis  7 . 
     It will be understood that changes in the details, materials, steps and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention. The foregoing description illustrates the preferred embodiment of the invention; however, concepts, as based upon the description, may be employed in other embodiments without departing from the scope of the invention. Accordingly, the following claims are intended to protect the invention broadly as well as in the specific form shown.