referring now to fig1 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 ( fig1 ) 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 ( fig2 ) 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 fig2 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 ( fig4 ), 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 fig5 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 .
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 .