Abstract:
Attachment structure for converting an integral implement to a pull-type implement includes wheel modules which can be placed at different locations along the frame to avoid interference with tool standards or other hardware. Each module includes both a forward gauge wheel and a rearward transport wheel. The transport wheels are located behind the center of gravity of the implement for stability, and the forwardly located gauge wheels offset the moment resulting from standard draft. A hitch storage jack doubles as a gauge wheel adjustment tool. To maintain the wheels in phase and provide a transport lock-up feature, a simple parallel circuit with pilot operated check valves on the base or lift end of each cylinder is utilized.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to agricultural implements such as rippers, and more specifically to wheel structure for such implements. 
     BACKGROUND OF THE INVENTION 
     Agricultural implements such as deep tillage rippers often are towed by a large four-wheel drive (4WD) tractor, especially if the implement is a larger unit with nine or more standards. A problem can arise when the operator desires to pull an integral ripper, which is normally mounted on a three point tractor hitch, since many 4WD tractors in the size range necessary are not equipped with such a hitch. It is often desirable to have a means of converting an integral ripper to a pull-type unit. Consequently, a drawn hitch attachment is needed for the larger sized rippers, and compatibility with smaller rippers such as those with five or seven standards is advantageous. 
     Numerous hitch attachments are available for converting an integral ripper to a pull-type ripper. Such attachments typically include a hitch assembly that pins into the existing lower hitch plates of the ripper. A turnbuckle is placed from the upper link attachment location on the ripper to an upper surface of the hitch to facilitate horizontal adjustment of the machine front-to-rear for compensating for different tractor drawbar heights. Independent wheel packages are generally placed off the front of the ripper, one on each side, with a forward acting wheel arm and dual tandem wheels. 
     Hitch attachments for conversion from integral to pull-type can produce some very undesirable conditions. A light hitch condition often results from placement of the majority of the implement weight behind the wheels, a condition that produces high vertical hitch loads on the tractor drawbar in the upward direction. The high vertical loads, in turn, produce high axial loads which pass through the turnbuckle. Other negative attributes of the forwardly located wheels include unstable transport conditions and high stresses on certain areas of the implement frame. A further problem with some wheel arrangements is instability or oscillation of the implement while operating in the field as the front of the frame tends to nose downwardly and then rock back upwardly under certain field conditions. 
     To eliminate some of the problems, placement of the transport wheels near the rear of the machine is helpful. However, numerous obstacles on the rear of the implement frame limit such wheel placement. Placement of the wheels at the rear of the implement creates undesirable moments tending to rotate the front of the frame downwardly. Maintaining proper machine attitude and uniform working depth is a problem. 
     Using wheels at both the front and the rear of the implement present numerous problems, including the provision of an economically feasible wheel lift and timing system. Hydraulical controls for all the wheels can be expensive and very complex. Manually adjustable gauge wheels often are difficult to fine tune, particularly when the implement is relatively large and heavy. Providing conversion hitch attachments therefore has presented numerous challenges to the implement designer. 
     A problem with independent wheel modules, regardless of wheel location, is need for structure to keep the wheels timed. A mechanical timing tube is often impractical because of interference with machine components. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an improved attachment structure for conversion of an integral implement to a pull-type implement. It is a further object to provide such a structure which overcomes most or all of the aforementioned problems. 
     It is another object of the present invention to provide an improved attachment structure for conversion of an integral implement to a pull-type implement which is relatively low in cost and complexity. It is yet another object to provide such a structure having improved stability, better depth control consistency, reduced stress and reduced front to rear instability or oscillation problems compared to at least most previously available structures. 
     It is a further object of the invention to provide an improved attachment structure for conversion of an integral implement to a pull-type implement having a compact, economical design which facilitates a variety of tool spacings without interference. It is another object to provide such a structure which is compatible with large implements such as rippers with up to nine standards or more as well as with smaller implements such as rippers with five or seven standards. 
     It is yet another object of the invention to provide an improved attachment structure for conversion of an integral implement to a pull-type implement, the structure having a rearward acting transport wheel and a forward acting gauge wheel. It is a further object to provide such a structure having a simple and inexpensive lift system. 
     Attachment structure described below for converting an integral implement to a pull-type implement includes wheel modules which can be conveniently mounted at different locations along the implement frame depending on the number and spacing of tools. Each module supports both a forward gauge wheel and a rearward transport wheel. The module includes a lower wheel bucket or channel, in which a rear wheel arm rotates, and an upper mast or tower. The tower captures the base end of a hydraulic cylinder used to raise and lower the rear transport wheels. The tower additionally contains a sliding mechanism for a front gauge wheel yoke. Mounting hardware secures each tower and bucket to the desired location on the front rank tube of the implement. 
     The transport wheels are located behind the center of gravity of the implement to provide a substantial improvement in stability and reduced frame stress. The placement of the wheels achieves the desired amount of downward force on the tractor drawbar. The forwardly located gauge wheels offset the moment resulting from the ripper standard draft that rotates the front of the implement downwardly to stabilize the machine in working conditions. Normal field working depth is set by lowering the machine into the ground to the desired depth using the hydraulically controlled rear wheels. Cylinder stops are then placed on the depth control cylinders, and the front gauge wheels lowered into contact with the ground. However, because of the weight and size of the implement, fine tuning the gauge wheel position requires considerable force. To economically provide the necessary mechanical advantage, the hitch storage jack is made to double as a gauge wheel adjustment tool. The jack slides onto a post mounted on the upper tower and pushes against a clip mounted on the side of the gauge wheel yoke. 
     To prevent the transport wheels on the wheel modules from getting out of phase, a hydraulic system includes a parallel circuit with pilot operated check valves on the base or lift end of each cylinder. The check valves lock hydraulic fluid into the base end of each cylinder and prevent uneven loads from changing the relative extension of the cylinders. The pilot is operated off the rod or lower end of each cylinder. Therefore, when the machine is lowered, the check valve opens and allows oil flow out of the base end. An orifice is used to provide the optimum breakoff pressure for the check valve. 
     The rearward placement of the transport wheels creates very stable transport conditions. The wheel modules can be widely spaced for additional stability. Working depth accuracy and machine stability in the field is greatly improved because of the spacing of the four wheels, and the combination of the front and rear wheel support during tillage operations reduces or eliminates the oscillations of the type wherein the frame noses downwardly and then rocks back upwardly. The rear wheels can be used to set the desired working depth hydraulically. The wheel structure provides excellent support for the frame when the implement includes rear mounted tools such as leveling wheels or rolling basket attachments. By mounting two independent wheels to each wheel module, costs and complexity are minimized. Utilizing the hitch storage jack for gauge wheel adjustment results in a unique, cost-effective and user-friendly drawn hitch attachment. The hydraulic system eliminates need for costly rephasing cylinders and avoids the high reaction forces of a traditional master-slave series circuit. If desired, the hydraulic lock-up valve normally used during storage and machine maintenance can be eliminated because the check valves provide the same function. 
    
    
     These and other objects, features and advantages of the present invention will become apparent to one skilled in the art upon reading the following detailed description in view of the drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front perspective view of a tillage implement with hitch and wheel module structure attached. 
     FIG. 2 is an enlarged front perspective view of one of the wheel module structures of FIG.  1 . 
     FIG. 3 is a side view of the implement of FIG. 1 in the lowered working position. 
     FIG. 4 is a view similar to that of FIG. 3 but showing the position of the wheels in the raised transport position. 
     FIG. 5 is a schematic of a hydraulic circuit for use with the tillage implement of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, therein is shown an implement  10  such as a ripper or similar deep tillage implement having a main frame  12  and conventional three-point hitch structure  14  adapted for attachment to a three-point hitch (not shown) on a tractor or other towing vehicle. The implement  10  is shown with attachments for conversion to a towed implement. A hitch  20  is pivotally connected at a rearward end to the lower two attaching points of the three-point hitch structure  14 . A standard towing connection  22  for attachment to the tractor drawbar is connected to the forward end of the hitch  20 . A leveling link  24  extends between the towing connection  22  and the upper connection of the three point hitch structure  14  to provide a generally rigid but adjustable hitch connection to the frame  12 . 
     The frame  12  as shown includes transversely extending front and rear frame members  32  and  34  connected by generally fore-and-aft extending frame members such as shown at  36  and  38 . Wing frame sections  40  and  42  are pivotally attached at the ends of the main frame  12  and are pivotable from the working position shown upwardly and inwardly to a folded transport position by wing lift assemblies  44  and  46 . The wing frame sections rest on frame-mounted supports  48  in the transport position. Ripper standards  50  (FIG. 1) or other earth-engaging tools are connected at transversely spaced locations to the frame members  32  and  34  and the wing frame sections  40  and  42 . The tools can include rear mounted rolling baskets or leveling wheels such as shown at  51  which tend to move the center of gravity of the implement rearwardly. 
     To provide frame support, lift and depth control functions when the implement  10  is converted from integral to towed, first and second wheel modules  52  and  54  are transversely spaced on the forward member  34  of the main frame  12 . The modules  52  and  54  are self-contained and are generally identical. Therefore, only the module  52  will be described in detail below. 
     The module  52  (FIG. 2) includes bracket structure  60  for attaching the module at selected one of various locations along the front frame member  34 , depending on the locations of the tools  50  and other hardware on the frame. The bracket structure  60  includes a downwardly and rearwardly opening lower channel member  62  having an apertured top  64  through which mounting bolts  66  extend. The apertures are spaced so that the bolts  66  are spaced in the fore-and-aft direction a distance approximately equal to the wall spacing on the frame member  34 , and additional apertures are provided to accommodate other frame tube sizes. The threaded ends of the bolts  66  project upwardly through corresponding apertures in a lower flanged section  68  of an upper tower member or mast  70 . Nuts  72  are threaded onto the ends and tightened to secure the bracket structure  60  at the selected location on the frame member  34 . 
     The forward end of a lift wheel arm  76  is pivotally connected at  78  between the sides of the channel member  62  for rocking between a generally horizontal raised working position and downwardly directed lowered transport position. The lower end of the arm  76  is bifurcated and rotatably mounts a lift wheel  80 . The lift wheel arm  76  includes a cylinder bracket  82  pivotally connected to the rod end  84  of a lift cylinder  86 . The base end of the lift cylinder  86  is pivotally connected to the upper aft end of the mast  70 . 
     The mast  70  includes transversely spaced sides  90  with a downwardly and rearwardly opening pivot area  92  pinned to the base end of the cylinder  86 . A rectangular arm guide area  96  extending diagonally upwardly in the rearward direction is defined between the mast sides  90  and a plate  98  connected between the top edges of the sides at forwardmost locations  100 . A mating gauge wheel arm  106  is slidably mounted in the guide area  96  for sliding diagonally relative to the mast  70 . The lower end of the gauge wheel arm  106  is connected to a yoke or wheel support  108  and rotatably mounts a gauge wheel  110  which extends downwardly and forwardly of the frame member  34 . 
     As shown in FIG. 2, the upper end of the arm  106  is located above the frame member  34  and adjacent pivot area  92  when the gauge wheel  110  is adjusted for maximum working depth. The lower, forward ends of the sides  90  include arcuate cut-out areas  120  for receiving a bight portion of the yoke  108 . The sides of the arm  106  are apertured at  116  to receive a pin  118  which extends through the selected set of apertures  116  and apertures in the spaced sides  90 . By aligning a different set of apertures  116  with the apertures for the pin  118 , the working height of the frame  12  can be adjusted. The depth adjustment range of the gauge wheel  110  is substantially less than the lift range of the lift wheel  80  between full retraction and full extension of the cylinder  86 . When the cylinders  86  are fully extended and the implement  10  is in the raised transport position (FIG.  4 ), the gauge wheels  108  are lifted from the ground, and the frame  12  is supported by the wheels  80  behind the center of gravity of the implement and by the forwardly extending hitch  20 . 
     Normal field working depth is set by lowering the frame  12  by retracting the hydraulic cylinders  86  to raise the rear transport wheels  80  until the tools  50  penetrate the ground to the desired depth. Cylinder stops (not shown) are then placed on the rods depth control cylinders or another standard stop arrangement to set the working position of the wheels  80  relative to the frame  12 . The pin  118  is removed to allow the gauge wheel arm  106  to slide downwardly and forwardly until the gauge wheel  110  is lowered into contact with the ground. To move the gauge wheel firmly into contact with the ground, jack structure  130  is provided. A standard hitch jack  132  is supported from one side  90  of the mast  70  by a side support member  134  extending between an outer tube of the jack  132  and the side  90 . A telescoping lower base section  138  of the jack  132  is supported from one side of the gauge wheel support  108  by a support bracket  140 . Rotation of a jack handle  142  extends the base section  138  to urge the gauge wheel downwardly against the ground. The operator then inserts the pin  118  through the apertures in the sides  90  and through the aligned set of apertures  116  in the gauge wheel arm  106  to secure in the gauge wheel in the adjusted working position. The gauge wheels  110  extend forwardly of the frame member  34  and offset the moment resulting from the tool standard draft that tends to rotate the front of the implement downwardly. 
     To prevent the transport wheels  80  on the wheel modules from getting out of phase as differing forces act on the cylinders  86 , a hydraulic system indicated generally at  150  in FIG. 5 is provided. The system  150  includes hydraulic lines  152  and  154  connecting the cylinder  86  of the first wheel module  52  in parallel with the cylinder of the second wheel module  54  to a controllable source of hydraulic fluid under pressure  156  on the towing vehicle. A pressure line  160  is connected through first and second pilot operated check valves  162  and  164  to the base or lift ends of the cylinders  86 . The rod ends of the cylinders  86  are connected to a return line  170  and provide fluid flow from the rod ends to reservoir as the cylinders  86  are extended. The source  156  can be a conventional hydraulic control system on a tractor with a selective control valve (SCV) or similar valve structure allowing for controlling flow and pressure in the lines  152  and  154 . When pressure is applied to the valves  162  and  164  through the line  160 , the check valves allow flow to the base ends so the cylinders  86  extend and move the transport wheels  80  downwardly relative to the frame  12 . 
     The check valves  162  and  164  include pilot lines  172  and  174  connected to the line  170 . When the operator wishes to retract the cylinders  86  to lower the frame  12 , the selective control valve (not shown) on the towing vehicle is operated to pressurize the rod end line  170  and return the line  160  to reservoir. Normally, the check valves  162  and  164  prevent return flow from the base ends of the cylinders  86 . However, when the fluid pressure in the line  170  reaches a valve breakoff level as sensed by the valves via the pilot lines  172  and  174 , the check valves will open to allow return flow from the base ends so the cylinders  86  can retract to lower the frame  12 . The check valves  162  and  164  prevent uneven loads on the cylinders  86  from changing relative extension of the cylinders so the cylinders remain in phase. Orifices  182  and  184  are inserted in the lines at the base ends of the cylinders  86  to provide the optimum breakoff pressure for the check valves  162  and  164 . Hydraulic lock-up valves normally used during storage and machine maintenance can be eliminated because the check valves  162  and  164  provide the same function. 
     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.