Abstract:
A rockshaft is mounted over the front rank of the implement frame and is operated by cylinders located at opposite ends of the rockshaft connected to lift arms extending radially adjacent bearing mounts. Fore-and-aft extending links aligned with the lift arms and mounts operate lift wheel assemblies. A hitch arm connected near the center of the rockshaft is directly connected to a hitch turnbuckle for level lift operation. An aligned arrangement of cylinders, cylinder brackets, links and arms provides minimal torsional loading, particularly when the rockshaft is rotated to fully raise the implement frame for transport and is in the most susceptible shock loading condition. Moment arms are controlled to minimize rockshaft torsional loading during highest stress conditions. The front-mounted rockshaft provides simplicity and advantageous weight distribution.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to agricultural implement frames and more specifically, to lift and leveling systems for such frames. 
     BACKGROUND OF THE INVENTION 
     Agricultural implement frames for pull-type implements such as tillage and seeding equipment or the like typically include a level lift rockshaft system. A rear-mounted rockshaft weldment connected to lift wheel assemblies is mechanically linked through a complex linkage arrangement to a hitch pivotally connected to the front of the frame. A bellcrank is connected through a link to the hitch. As the rockshaft is rotated to change the position of the lift wheels relative to the frame, the implement is raised and lowered and the linkage arrangement pivots the hitch to maintain the frame in generally a level condition. 
     Most level lift rockshaft systems have a relatively large number of parts and wear points. As a result, such systems are usually heavy and expensive. A large number of wear points make such a system somewhat unreliable. The conventional aft location of the heavy rockshaft structure detrimentally shifts considerable weight to the rear of the implement. Torsional windup of the rockshaft is also a common problem, and the rockshaft must have a substantial wall thickness to withstand the torsional forces and prevent windup, a requirement which adds to the weight and expense of the implement. The rockshaft is subject to extreme shock loading, particularly when the implement is fully raised to a transport position. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an improved rockshaft system for an implement. It is another object to provide such a system which overcomes most or all of the aforementioned problems. 
     It is a further object of the invention to provide an improved rockshaft system for an implement which is less expensive to manufacture, more reliable in operation and more advantageous in weight distribution than at least most previously available rockshaft systems. It is another object to provide such a system which has reduced rockshaft windup, less complex mounting and linkage structure and fewer wear points. 
     It is a further object of the invention to provide a relatively low cost implement frame with an economical level lift rockshaft system, better weight and load distribution, and fewer wear points than at least most previously available implement frames. 
     A rockshaft is mounted over the front rank of the implement frame and operated by cylinders located at opposite ends. Each cylinder is connected to a lift arm extending radially from an end of the rockshaft which also is directly connected to a fore-and-aft extending link which operates trailing lift wheel modules connected to the frame. A hitch arm connected near the center of the rockshaft is directly connected to a hitch turnbuckle for level lift operation without need for a complicated bell crank structure. The use of the two end cylinders with direct coupling of the lift linkages facilitates use of a parallel/series type of hydraulic circuit with torsional forces resulting from the hitch leveling forces only. Three or more adjustably locatable sets of rockshaft bearing mounts connect the rockshaft to the front tube of the implement frame at locations substantially aligned with hitch and lift arms. The arrangement of cylinders, supports and arms provides minimal torsional loading, and therefore a thinner walled tube can be used to reduce cost and weight. When the rockshaft is rotated to fully raise the implement frame for transport and is in the most susceptible shock loading condition, the torsional loading is minimized, greatly reducing stress and improving the reliability of the frame and lift system. The reduced number of components, improved loading characteristics, and improved weight distribution provide a cost effective, strong and reliable implement frame. 
    
    
     These and other objects, features and advantages of the invention will become apparent from the description below in view of the drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a multi-section tillage implement with a lift and level system. 
     FIG. 2 is an enlarged perspective view of the center frame section of the implement of FIG. 1 with portions removed. 
     FIG. 3 is a side view of the a portion of the center section of the implement of FIG. 1 
     FIG. 4 is a view similar to that of FIG. 3 but showing the implement in a raised transport position. 
     FIG. 5 is a front view of a portion of the implement of FIG.  1 . 
     FIG. 6 is a schematic representation of the hydraulic circuit for the lift system of the implement of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, therein is shown a portion of an agricultural tillage implement  10  having a center or main frame  12  and wing frames  14  and  16  pivotally connected to the outer ends of the main frame by pivot structure  18 . The main frame  12  is supported by lift wheel modules  20  and  22 . The wing frames include wheel modules  24  and  26  which support the wing frames  14  and  16 , respectively. A front hitch assembly  30  connects the implement  10  to a towing vehicle (not shown) for forward movement F over the ground. A trailing hitch assembly  32  facilitates connection of a spray trailer or other trailing implement to the rear of the frame  12 . Tools  34  are supported from the frames  12 ,  14  and  16  for working the soil. As shown in FIG. 1, the implement  10  includes outermost wing structures  36  and  38  which are hinged to the wing frames  14  and  16 . 
     The main frame  12  includes a front transversely extending beam or tube  42  and a rear tube  44  connected by fore-and-aft extending inner beams  48  and  50  and outermost beams  54  and  56 . Intermediate transversely extending frame members or ranks  60 ,  62  and  64  are located between the front and rear tubes  42  and  44 . Brackets  66  and  68  depend from the front tube  42  and pivotally support the aft end of two forwardly converging hitch beams  72  and  74  the front hitch assembly  30  on opposite sides of the centerline of the implement  10 . The forward ends of the beams  72  and  74  are joined to a hitch connector  78 . 
     A rockshaft  80  is rotatably supported directly above the forward tube  42  for rotation about an axis parallel to the tube by narrow outer pivot brackets  84  and  86  and a narrow central bracket  88  (FIG.  2 ). An upwardly extending central arm  90  is fixed to central portion of the rockshaft  80  immediately adjacent the central bracket  88 . An adjustable length fore-and-aft extending leveling link  92  has an aft end pivotally connected to the outermost end of the central arm  90 . The forward end of the link  92  is pivotally connected to the hitch connector  78  so that as the rockshaft  80  is rotated, the angle of the hitch assembly  30  relative to the main frame  12  will change. 
     The outer pivot brackets  84  and  86  are located adjacent the opposite ends of the rockshaft  80 , and arms or masts  94  and  96  are connected to the rockshaft immediately adjacent the brackets  84  and  86 , respectively. Angle brackets  104  and  106  include forward ends connected to the pivot brackets  84  and  86  and aft ends connected to the transverse frame members  64  by U-bolts  108 . A central angle bracket  110  includes a forward end secured by U-bolts  112  to the forward tube  42  immediately adjacent the pivot bracket  88  and an aft end connected to the member  64  by U-bolts  114 . 
     Hydraulic cylinders  120  and  122  have base ends connected to the aft ends of the brackets  104  and  106  over the frame members  64 . The rod ends are connected to the arms  94  and  96  for rotating the rockshaft  80  as the cylinders are extended and retracted. The lift wheel modules  20  and  22  include downwardly and forwardly directed wheel arms  130  and  132  pivotally connected by transversely adjustable brackets  136  and  138  to selected spaced locations on the rear tube  44 . Mast arms  140  and  142  project upwardly above the frame  12  from the lift arms  130  and  132  forwardly adjacent the arm pivot locations. Fore-and-aft extending links  144  and  146  are pivotally connected between the upper ends of the mast arms  140  and  142  and the upper ends of the forward rockshaft masts  94  and  96 , respectively. As the cylinders  120  and  122  are extended, the masts rotate forwardly to pivot the wheel arms  130  and  132  downwardly to lift the frame  12 . At the same time, the hitch assembly  30  is pivoted downwardly to facilitate leveling of the implement. 
     As shown in FIG. 1, the wheel modules  24  and  26  on the outer frames  14  and  16  include lift cylinders  154  and  156  connected in a parallel/series circuit  160  (FIG. 6) with the cylinders  120  and  122 . The cylinders  154  and  156  are connected between module support bracket structures  164  and  166  adjustably mounted on selected frame tubes and the forward ends of lift arms  168  and  170 . Adjustable links  174  and  176  extend forwardly from the bracket structures  164  and  166  to connections  178  and  180  with forward ranks. By varying the lengths of the links, the positions of the wheels on the modules  24  and  26  relative to the frame can be adjusted to provide frame leveling and the like. FIG. 1 illustrates the flexibility of the wheel module system which permits the wheel locations to be selected to accommodate various tool and hardware locations and spacings on different implement frame layouts. 
     The hydraulic circuit  160  as shown in FIG. 6 includes conventional control valve structure indicated at  190  located on the towing vehicle connected to a source of hydraulic fluid under pressure  192  on the vehicle. A hydraulic line  194  connects the base ends of the main frame lift cylinders  120  and  122  to the valve structure  190  via transport lock valve  196  and a normally open single point depth control (SPDC) valve  198  (FIG.  4 )having an actuator  199  for moving the valve to a flow blocking position when the cylinder  120  retracts to a preselected position to provide a depth control stop function. Such a depth control structure, for example, is described in copending and commonly assigned application Ser. No. 10/281,443 filed Oct. 25, 2002 and entitled DIRECTLY ACTUATED DEPTH CONTROL. 
     The rod end of the cylinder  120  is connected through a line  200  to the base end of the wing lift cylinder  156  so that the cylinder  156  operates in series with the cylinder  120 . Similarly, the rod end of the cylinder  122  is connected via line  202  to the base end of the cylinder  154  for series operation of the cylinders  154  and  122 . The rod ends of the cylinders  154  and  156  are connected together and to the valve structure  190  through a line  206 . 
     In operation, assuming the cylinders  120 ,  122  and  154 ,  156  are fully extended, the wheel modules support the implement frame in a raised transport position. The SPDC valve  198  is in the open position when the frame is raised above the set field-working position. With the transport lock valve  196  (FIG. 6) in the open non-blocking position, the operator moves the valve control structure  190  to open the lines  194  to reservoir so that the cylinders  120  and  122 , and the cylinders  156  and  154  connected in series with the cylinders  120  and  122 , retract. The cylinders retract substantially in unison until SPDC valve  198  is closed by depression of the actuator  199  to block the line  194  and prevent further lowering of the frame. The valve  198  is adjustable to vary the working depth of the tools  34 . 
     To raise the implement  10  while in the lowered working position, the operator moves valve  190  to pressurize the line  194 . A one-way check valve in the valve  198  permits flow to the base end of the cylinders  120  and  122  when the valve  198  is in the blocking position so the cylinders can extend and raise the implement frame. As the cylinders  120  and  122  extend, fluid exiting the rod end of the cylinder  120  causes the wing cylinder  156  to extend in unison with the cylinder  120 . Fluid from the rod end of the cylinder  122  extends the cylinder  154  to provide a level lift. For transport, the cylinders  120  and  122  are fully extended, and the valve  196  can be moved to the closed position to lock the cylinders in the extended position. 
     By operating the cylinders  120  and  122  in parallel at the opposite ends of the rockshaft  80  and generally in line with the corresponding lift linkage structures (see FIGS. 2 and 5) for the wheel modules  20  and  22 , torsional forces in the rockshaft are minimized. Therefore, a lighter rockshaft can be used compared to that necessary for a conventional lift arrangement. In addition, the forward mounting of the rockshaft  80  on the frame  12  facilitates direct connection of the hitch leveling link  92  to the rockshaft arm  90 . The brackets  84 ,  104  and  86 ,  106  are narrow and transversely adjustable on the implement frame to limit interference and provide a wide range of tool, hardware and lift and leveling linkage mounting flexibility. Frame stress from cylinder operation is also reduced through use of the brackets and the alignment of lift linkage components described above. 
     In the raised transport position, moment arms through which forces from the from the lift wheel structure and the leveling link act are minimized to reduce torsional loading on the rockshaft. For example, in a maximum stress condition when the wheels of the lift wheel module  20  are lowered (FIG. 4) and the front of the hitch assembly  30  is pivoted downwardly to level the implement for transport, the moment arm through which the forces transferred through the hitch link  92  is very small since the mast  90  is approaching alignment with the axis of the link  92 . Therefore, only a small torsional moment is transferred from the hitch structure  30  to the rockshaft  80  in the transport position. The moment arms through which forces in the links  144  and  146  act on the rockshaft  80  are also at a minimum in the transport position. Typically, the masts  94  and  96  are operated either in the fully forward position (FIG. 4) for transport or in the rearward position (FIG. 3) for field-working operations when stresses are largest. Therefore, the time that the rockshaft  80  is in a position wherein the moment arms are substantially upright and define maximum moment arms is minimal and usually occurs midway in the lift or lower cycle when stresses are less. 
     Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.