Abstract:
A mulch tiller or similar implement having a rigid frame supporting a plurality of forward trash-sizing gang assemblies and rearward plow tools. Spring brackets rockably support the gang asemblies for independent vertical movement with respect to the frame and maintain a generally constant down pressure of the gangs against the soil. The frame includes diagonal beam structure and a lower subframe assembly for compact shipping, good draft load distribution and underframe clearance. Common depth control, main frame and hitch components are utilized for implements of varying widths to reduce cost.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to a tillage implement and more specifically to a tillage implement with disk or coulter gang assemblies. 
     Tillage implements having both forward disk or coulter gang assemblies and rearward plow tools such as twisted shovels or cultivator sweeps are commonly used in stubble-mulch and deep fallow tillage operations. Disk or coulter blades cut the stubble or stalks and trash ahead of the plow tools, and the plow tools rip down through the plow-soil layer to open the soil so air and water can get in. Such implements leave the surface of the soil open and blended with residues that protect the topsoil. The residues decompose faster into humus, and thereby create drought resistance and stronger crop root growth the following year. The soil surface is left moderately ridgy to give moisture a chance to soak in rather than run off. Wind erosion is kept to a minimum by the crop residue and the ridges left by the plow tools. The commercially available John Deere 1710 Mulch Tiller is an example of such a tillage implement. 
     A typical mulch tiller or similar type implement includes disk or coulter gang assemblies which are supported at the forward end of a main frame assembly. Tool-carrying shank assemblies are mounted at the rearward portion of the main frame. Changing the relative depth of the gangs and the standard assemblies required changing the relative height of the front and rear portions of the frame. In addition, a leveling adjustment is required on the front hitch assembly to maintain the proper attitude of the entire frame assembly both in the transport and in the field-working positions. 
     The gangs on the aforementioned implements are either mounted relatively ridgidly with respect to the frame assembly or else are mounted with spring assemblies providing a short tripping distance with the downward force exerted by the trip assemblies increasing significantly as the gangs move upwardly and closer to the frame. Such gang mounting arrangements result in uneven penetration of the disks or coulters, and when rough terrain or obstacles are encountered, upward movement of the gangs can actually lift the frame or remove a significant portion of the weight from the frame so that the rear tools do not penetrate to the desired level. The previous implements are difficult to balance, that is, to provide a nearly constant down force both at the rear and front portions of the frame in varying soil conditions and terrain. The relative inflexibility of the gangs results in the individual blades or coulters supporting a disproportionate amount of the implement weight. It is not uncommon for disks or coulters or gang bearings to break. The front portion of the frame often has to be adjusted with respect to the rear portion to maintain both the proper cutting action of the disks or coulters and to maintain the proper penetrating depth of the earth-working tools as soil conditions change. With the previous implement designs which utilize a main frame assembly with relatively adjustable front and rear portions, wide implements could not be practically designed since the adjustable frame portions cannot easily accommodate pivotally connected outrigger sections. 
     It is therefore an object of the present invention to provide a tillage implement with improved trash-sizing and soil-penetrating characteristics in various soil conditions and terrain. It is a further object to provide such an implement which has improved trash and soil flow for better incorporation. 
     It is a further object to provide a tillage implement with forward trash-sizing gangs and rearward earth-working tools wherein the weight of the total implement is properly distributed on both the gangs and the rear tools, even in rough terrain and varying soil conditions. It is another object to provide such an implement utilizing forward coulter or disk gang assemblies rockably mounted on the frame which provide reliable trash sizing relatively independently of the distance between the frame and the surface of the soil. 
     It is another object of the invention to provide a disk or coulter gang assembly wherein the gang is spring loaded downwardly and can trip up over obstacles, and wherein a relatively constant level downward force is maintained regardless of the trip position of the gang. It is another object to provide a disk or coulter gang assembly which can accommodate rough terrain or variations in soil conditions better than previously available gangs, and which provides a reduced incidence of breakage in the gang assembly. 
     It is still another object of the present invention to provide a tillage implement which can accommodate either straight coulter or angled disk gangs of various widths, but which still utilizes a standard main frame, depth control, and hitch assembly to reduce manufacturing costs and permit convenient modification of the working width of the implement. 
     It is yet another object of the present invention to provide a trash-sizing and soil-penetrating implement which includes disk or coulter gang assemblies, wherein the implement has a main frame which easily accommodates added weights without significantly affecting the down pressure on the gangs and without significantly reducing underframe clearance. 
     It is another object of the invention to provide an improved frame assembly for a multiple-tool tillage implement. It is a further object to provide such a frame with diagonal structure in line with the forward hitch to provide a strong backbone for the implement while at the same time maintaining good underframe clearance. 
     It is still another object of the invention to provide an improved tillage implement with trash-sizing and soil-penetrating tools wherein lift and leveling linkages are maintained substantially below the level of the main frame. 
     It is yet a further object of the invention to provide a compact, stable trash-sizing and soil-penetrating implement which uses a single main frame and which requires fewer leveling adjustments than at least some of the previously available implements. 
     It is another object to provide such an implement with an improved frame which is easier to package for shipment and to assemble than previously available frames. 
     In accordance with the above objects, a rectangular, substantially rigid main frame assembly includes a forward portion supporting a plurality of transversely spaced disk or coulter gang assemblies. Each assembly includes at least two spring trip bracket units connected to the frame and supporting a generally transverse gang tube. Standards extend downwardly and rearwardly from the gang tube and terminate in disk gang bearings which rotatably support the disk or coulter gang. The spring bracket permits the gang tube to be torqued upwardly as forces act against the disks or coulters. The geometry of the spring bracket provides a relatively constant trip force between the lowermost and uppermost positions of the disk gang therefore making the down pressure on the gang relatively independent of the distance between the main frame and the top of the soil. The spring brackets may be connected directly to the front transverse bar of the main frame when a transverse arrangement of coulters is utilized. Alternatively, stub-bars can be bolted to the fore-and-aft components of the main frame to support individual disk gangs at an angle, preferably approximately fourteen degrees from the transverse direction. 
     The rear portion of the frame supports a plurality of transversely spaced heavy-duty spring trip shank assemblies carrying deep penetration tillage tools. The standards have a high initial trip force level, and the level first increases as the standard trips upwardly. After reaching an intermediate tripped position, the trip force begins decreasing to permit large obstacles to be cleared. The initial increase in trip force provides for positive reentry of the earth-working tool. Concave twisted shovels are provided on the spring trip shank assemblies for improved soil flow and trash incorporation. The individual tripping action coupled with the level trip force curve of the gang assemblies provide a substantially uniform and properly distributed down force on both the disks or coulters and the earth-working tools to properly size trash and to maintain constant deep soil penetration of the shovels, even in rough terrain or where obstacles are encountered. 
     The frame includes upper diagonal beam structure and a lower weldment which can be compactly packaged for shipment and easily assembled. Good ground clearance is provided beneath the frame. The lift assembly and leveling linkages are primarily contained below the top of the frame for a neater appearance and for more positive depth adjusting action. The upper diagonal beam structure forms a natural extension of the forward hitch for good draft load distribution along the frame. Suitcase-type weights can be conveniently supported on the beam structure in an accommodation space defined by the rearward portion of the frame. The gang support arrangement including the spring brackets provides a relatively even down pressure on the disk or coulter gangs to provide uniform trash sizing in differing terrain and soil conditions. The constant down pressure together with the ability of an individual gang assembly to trip independently of the remainder of the gangs advantageously maintain a relatively constant down pressure for the earth-working tools, even when additional weights are added. Disks or coulters can move upwardly over relatively large obstacles and are less likely to break. Disk scrapers are supported by the gang tube rather than by an individual scraper support bar so that the distance the gangs can trip is increased by eliminating the interference that existed between the frame and support bar with at least some of the previous implements. 
     The present design permits use of either angled disk gangs or straight blade coulter gangs of numerous different widths utilizing the same depth control, main frame and hitch components. The main frame structure easily accepts folding outrigger sections so that relatively wide implements can be manufactured. In a folding implement where more than one angled disk gang assembly is utilized on a flexible pivoting outrigger frame, the gangs are angled in opposite directions to balance side forces. 
     These and other objects, features and advantages of the present invention will become apparent from the detailed description below when taken with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top view of an implement embodying the principles of the present invention. 
     FIG. 2 is a rear view partially in section of a disk gang assembly. 
     FIG. 3 is a side elevation of the disk gang assembly of FIG. 2. 
     FIG. 4 is a rear view of a coulter gang assembly. 
     FIG. 5 is a side view of the coulter gang assembly of FIG. 4. 
     FIG. 6 is an exploded fragmentary view of the main frame and lift and leveling assemblies of the implement of FIG. 1. 
     FIG. 7 is a side view of the lift assembly and leveling linkage for the implement of FIG. 1 with the frame in the field-working position. 
     FIG. 8 is a view similar to FIG. 7 but showing the frame in the transport position. 
     FIG. 9 is a top view of the right-hand portion of an implement similar to that shown in FIG. 1 but showing the frame outfitted with gangs for a narrower field-working width. 
     FIG. 10 is a view similar to FIG. 9 but showing an implement with a flexible pivoting outrigger section utilizing two disk gang assemblies offset at opposite acute angles with respect to the transverse direction to equalize side forces on the outrigger section. 
     FIG. 11 is a top view of a portion of a folding implement with a rigid outrigger section. 
     FIG. 12 is a top view of a portion of an implement similar to the implement of FIG. 1 but utilizing coulter gang assemblies. 
     FIG. 13 is a top view of an implement similar to that of FIG. 12 but having a narrower outer coulter gang assembly supported by two rather than three spring bracket assemblies. 
     FIG. 14 is a perspective view of a portion of the rear section of the implement of FIG. 1 showing the heavy-duty spring trip standard assembly with a concave twisted shovel in the soil-working position. 
     FIG. 15 is a view of the suitcase weights taken along lines 15--15 of FIG. 1. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, therein is shown a tillage implement 10 having a rigid, generally rectangularly shaped main frame 12 supported for forward movement over a field by vertically adjustable wheel assemblies 14. A hitch assembly 16 is connected to the forward portion of the main frame 12 and includes a forward towing connection 18 adapted for connecting to a tractor or other towing vehicle. The forward portion of the main frame 12 supports a plurality of transversely spaced trash-sizing gang assemblies 20 for chopping or cutting stubble, crops or crop residue. The rearward portion of the main frame 12 supports a plurality of earth-working tools indicated generally at 22 for penetrating the soil and for lifting the soil to partially cover the material cut by the gangs 20. The earth-working tools 22 are preferably deep tillage tools such as chisel plow shovels which typically penetrate at least six to twelve inches below the surface of the soil. 
     The trash-sizing gang assemblies 20 preferably include disk gangs 26 (FIGS. 1-3) having a plurality of cup-shaped disks 28. In the preferred embodiment, at least four disks but no more than nine disks are transversely supported on a gang bolt 30 with spacers 32 maintaining the desired separation between the disks. The gang 26 is rotatably mounted by disk bearings 34 located at the lower ends of arms or standards 36 which depend from a rectangular gang tube 40. The gang tube 40 in turn is supported from the forward portion of the main frame 12 by a plurality of spring bracket assemblies 42 which permit the gang 26 to rock rearwardly and upwardly relative to the frame 12 over a range of heights while maintaining a constant down pressure of the gangs 26 against the soil when the frame is in the soil-working position. 
     The spring bracket assembly 42 includes a rearwardly opening channel-shaped main bracket 44 having a forward right-angle notch 46 which is received against a rectangular tube 48 connected to the main frame 12. A U-bolt 50 is tightened against the tube 48 and the main bracket 44 to secure the bracket in the desired location. The bracket 44 has a lower portion 52 which extends below the main frame 12. The bracket 44 extends rearwardly and upwardly from the tube 48 to an apertured spring-abutting surface 54 which is angled downwardly and forwardly. A fore-and-aft extending pivot bracket 56 is connected at its forward end by a transverse pivot 58 to the lower portion 52 of the main bracket 44. The lower portion of the bracket 56 includes downwardly-protruding ears 60, which as best seen in FIG. 3, receive the top portion of the gang tube 40. A pair of connecting bolts 62 extend downwardly between each pair of ears 60 adjacent opposite faces of the gang tube 40. The bolts 62 pass through a plate 64 located on the upper end of the standard 36. The bolts 62 are tightened to draw the plate 64 against the generally horizontal bottom surface of the gang tube 40 and to secure the top portion of the gang tube against the bottom of the pivot bracket 56. The gang tube 40 is located below and behind the pivot 58, and, as the pivot bracket 56 rocks upwardly, the gang tube 40 will rock rearwardly and upwardly. 
     The pivot bracket 56 extends rearwardly from the area of connection with the gang tube 40 to a connection with a spring-retaining pivot 70. The pivot 70 includes a pivot pin 72 extending transversely outwardly through apertures 73 in the opposite sides of the pivot bracket 56. The pivot 70 also includes an upwardly directed, spring-abutting surface 74. A coil spring 76 is compressed between the spring-abutting surfaces 54 and 74, and a tension link or bolt 78 is inserted through the aperture in the surface 54 and is threaded into the spring-retaining pivot 70. The bolt 78 includes a head or upper enlarged surface 80 which prevents the bolt from sliding downwardly through the aperture in the surface 54. The bolt 78 maintains the spring 76 in a compressed condition and limits the downward pivoting of the bracket 56. In the embodiment shown in FIG. 3, the aperture 73 is slotted so that the spring-retaining pivot 70 can be moved to change the effective moment arm through which the spring 76 acts to bias the pivot bracket 56 downwardly to force the gang 26 against the soil. The pin 72 is located slightly below the pivot 58 and forwardly of the spring-abutting surface 54, so that as the gang 26 trips upwardly, initially the moment arm through which the spring 76 acts (M 1  of FIG. 5) increases, and thereafter the moment arm decreases (towards M 2 ) as the pin 72 moves through an arc about the pivot 58 towards location 75. The effective moment arm through which the rearward and upward forces on the gang 26 act, coupled with the effective moment arm of the pivot bracket 56 through which the compressed spring 76 acts, cooperate with the weight of the disk gang assembly 20 to provide a generally constant down pressure as the gang 26 rocks between its lowermost position determined by the length of the tension link or bolt 78 and the uppermost position which in the preferred embodiment is approximately eight inches above the lowermost position. In the preferred embodiment, the average working range of the gang 26 is approximately centered between the uppermost and lowermost positions. Although the curve of gang down pressure versus rocked position of the gang is generally constant, the trip geometry provides a slight down pressure peak in the average working range. 
     At least two spring bracket assemblies 42 are utilized for each trash-cutting gang assembly 20. The gang tube 40 is rigid and evenly distributes the torque acting thereon between the pivot brackets 56. For longer gangs 26 which include up to nine blades 28, (FIGS. 4 and 12) three spring bracket assemblies 42 are utilized. Down pressure is adjusted by changing the location of the pivot 72 in the slot 73 (FIG. 3), or by providing a plurality of springs 76 with different spring rates and selecting the spring to achieve the desired bias. 
     A plurality of scraper assemblies 90 are supported directly on the gang tube 40 to thereby eliminate the need for a separate scraper mounting bar or angle which would interfere with the frame and limit the trip height of the gang 26. Each scraper assembly 90 includes a scraper arm 92 pivotally connected to the front and rear faces of the gang tube 40. A plate 94 is connected for rocking with the arm 92 at a location offset rearwardly from the pivotal connection of the arm with the rear face. The arm 92 extends downwardly to a lower end which supports a scraper blade 98 adjacent the inside concave surface of the disk blade 28. A spring 100 is tensioned between opposite corners of adjacent plates 94 to bias the scraper blades 98 toward the corresponding disk blades 28. The plates 94 are slotted at 102, and bolts 104 inserted through the slots and into the gang tube 40 limit the angle through which the arms 92 pivot. 
     In the embodiment shown in FIG. 1, the tubes 48 to which the spring bracket assemblies 42 are attached are part of stub-bar structure 110. The stub-bars 110 are connected to the main frame 12 at an acute angle with respect to the transverse direction to thereby angle the gang tube 40 and the gang 26 with respect to the transverse direction. Preferably the acute angle is approximately fourteen degrees. The stub-bars 110 are welded to mounting plates 114 which in turn are bolted to opposite sides of fore-and-aft extending portions of the main frame 12. The ends of the stub-bars 110 corresponding to the trailing portion of the gang assemblies 20 are reinforced with L-shaped brackets 116 connected between the stub-bar end and a first transverse beam 120 which extends substantially across the width of the implement. In an alternate embodiment (FIGS. 4, 5, 12 and 13) the gang assemblies 20a have coulter gangs 26a rather than disk gangs. The gangs 26a each include from three to nine coulter blades 28a. The gang assemblies 20a are supported from the forward portion of the main frame 12 with the axes of rotation of the coulter blades 28a extending substantially parallel to the transverse direction. The support arrangement for the coulter gang assemblies is generally identical to that described for the disk gang assemblies 20 and so will not be discussed in detail. The scraper assemblies 90a for the coulter gangs 26a include L-shaped straps 130 connected to the gang tube 40 by bolts 132. The straps 130 are centrally positioned between pairs of coulters 28a to prevent dirt buildup. 
     The earth-working tools 22 are transversely spaced on a second transverse beam 140 which forms the rear of the main frame 12, and on third and fourth transverse beams 142 and 144, respectively, located between the beams 120 and 140. Additional tools 22 may be connected outwardly of the main frame 12 on extention or stub-frames 150 bolted to the main frame 12. In the preferred embodiment, the earth-working tools 22 include concave twisted chisel plow shovels 151 (FIG. 14) having a forwardly concave soil-directing path extending substantially the entire length of the shovel. For a more detailed description of the shovels 151, reference may be had to U.S. Pat. No. 4,275,792, issued June 30, 1981 and assigned to the assignee of the present invention, incorporated herein by reference. The twisted shovel 151 is supported at the lower end of a spring trip standard assembly 152 and includes a tip 153. The standard assemblies 152 are connected to the main frame 12 by U-bolts 154. The assembly 152 includes a standard 156 pivotally connected to a main bracket 158 and biased downwardly by a spring arrangement 159. In the preferred embodiment the standard assembly 152 has a high initial trip force level of greater than 800 pounds and preferably approximately 1,200 pounds. The trip force increases as the standard 156 trips up over obstacles to an intermediate position. From the intermediate position to a maximum tripped position the trip force decreases to permit the standard to easily clear the obstacle. 
     For a more detailed description of the assembly 152, reference may be had to co-pending application Ser. No. 326,735, entitled &#34;Spring Trip Standard Assembly&#34; of J. David Long and Phillip E. Stevens, assigned to the assignee of the present invention and incorporated herein by reference. The tip 153 of the concave twisted shovel 151 includes a lowermost centrally located portion, which when the main frame 12 is in the soil-working position, is supported approximately six to twelve inches below the surface of the soil. The depth of penetration of the tool 151 can be varied by raising or lowering the frame 12 on the ground wheel assemblies 14 within a preselected range of heights above the surface of the ground. Since the main frame 12 is rigid, the front portion of the frame will raise and lower also, but the spring bracket assemblies 42 permit the gangs 20 to rock and remain in contact with the soil throughout the range. In the preferred embodiment the gangs 20 can flex up to eight inches above the preselected lowermost position and typically work in a range of two to ten inches above the depth of the tool 151. The trip curve of the spring trip standard assembly 152, wherein the ratio of the maximum trip force to the initial trip force is less than about 1.5 to 1, maintains the tip 153 of the tool 151 at the proper depth without needless tripping and yet permits the shank 156 to trip upwardly over fairly large obstacles when necessary. The weight of the implement 10 is properly balanced between the front and rear portions of the main frame 12 so that the down force on the earth-working tools 22 remains fairly constant even as the trash-sizing gang assemblies 20 rock up and down over rough terrain and obstacles. 
     The main frame 12, as best seen in FIGS. 1 and 6-8, includes a lower rigid weldment or subframe 160 (FIG. 6) and upper rearwardly diverging diagonal beam members 162. The weldment or subframe 160 includes the first, third and fourth transverse beams 120, 142 and 144, respectively, maintained in a spaced relationship by a pair of rearwardly diverging, interconnecting beams 164 extending between the first and third transverse beams 120 and 142, and by similar interconnecting beams 166 extending between the third and fourth transverse beams 142 and 144. An additional pair of fore-and-aft interconnecting beams 168 extend between the first and third transverse beams 120 and 142 transversely outwardly of the interconnecting beams 164. The diagonal beam members 162 extend parallel to and directly overlie the interconnecting beams 164 and 166. Front and rear brackets 170 and 172, respectively, are welded to the lower surface of the rectangular beam members 162, and, together with U-bolt assemblies 174 extending around the weldment 164 at the connections of the third and fourth transverse beams with the interconnecting beams 164 and 166, secure the beam members 162 in overlying fashion above the diagonal beams 164 and 166. 
     Hitch drops 180, including a pair of side plates 182, on either side of the forward portions of the interconnecting beams 164 and the diagonal beam members 162 extend downwardly and forwardly to lower pivots 184. Bolts are inserted through holes in the plates 182 and through holes 185 in the interconnecting beams 164 and diagonal beam members 162. Plates 186 welded to the front portions of the diagonal beam members 162 extend downwardly across the forward face of the transverse beam 120 and are bolted to an angle 188 forming the forward face of the hitch drops 180. A transverse reinforcing beam 190 is bolted to the inside plates 182 of the hitch drops 180 below the beam 120. 
     The hitch assembly 16 includes a pair of forwardly converging hitch beam members 200 connected to the frame 12 by the pivots 184 of the hitch drops 180 below the plane of the lower portion of the weldment 160. A transverse hitch reinforcing beam 202 is connected between the hitch beams 200 to form a generally A-shaped hitch structure with the towing connection 18 located at the apex on the fore-and-aft center line of the main frame 12. 
     The ground wheel assemblies 14 include wheel support arms 210 (FIG. 6) which extend downwardly and rearwardly from a rectangular tubular shaft 212 rockably connected by brackets 214 to mating brackets 216 welded to and extending forwardly from the third transverse beam 142 adjacent the beams 164 and 168. Cylinder anchors 220 are welded to the top of the beam 142 and to the tops of the beams 168. Cylinder brackets 222 are welded to the lower ends of the wheel support arms 210 adjacent wheel frame pivots 224. A pair of hydraulic cylinders 226 have their anchor ends connected to the cylinder anchors 220 and their rod ends connected to the cylinder brackets 222. The cylinders 226 are connected to a source of hydraulic fluid pressure on the towing vehicle for extending and retracting the rod to rock the wheel arms 210 and the shaft 212 to raise and lower the wheel frame pivots 224 with respect to the main frame 12. The wheel frame pivots 224 support a pair of tandem wheel support frames 230 (FIG. 1) which diverge outwardly from a forward position between the third and fourth transverse beams 142 and 144 to a rearward portion located rearwardly and outwardly of the fourth transverse beam 144. Front and rear wheels 236 and 238, respectively, are rotatably supported at the ends of the support frame 230. The wheels 236 and 238 can rock up and down with respect to each other about the frame pivot 224. The fourth transverse beam 144 terminates inwardly of the rear wheels 238. The second transverse beam 140 is supported behind the rear wheels 238 by end brackets 240 welded to and extending downwardly from the rear ends of the diagonal beam members 162. The top of the beam 140 is generally parallel to the bottom of the diagonal beam members 162 so that the transverse beams 120, 142, 144 and 140 lie in approximately the same horizontal plane. 
     To maintain the main frame 12 in a substantially level position as the frame is rocked up and down between the field-working and transport positions, a frame leveling system 250 (FIGS. 6-8) is operably connected between the rock shaft 212 and the hitch assembly 16. An arm 252 extends upwardly and forwardly from, and is connected for rocking with, the rock shaft 212. Pivot plate structure 254 is supported for rocking at the forward end of the main frame 12 by a bracket assembly 256 connected to the transverse beam 120. A turn buckle 258 is connected at one end to the upper front portion of the pivot plate 254 by a pin 260. The lower portion of the turn buckle is connected by a pin 262 to a bracket 264 extending rearwardly from the transverse beam 202. A connecting link 266 is pivotally connected to the upper end of the arm 252 and to the lower portion of the pivot plate 254 for rocking the latter up and down as the rock shaft 212 is rocked by extension and retraction of the hydraulic cylinders 226. As the shaft 212 is rocked to raise the frame 12, the arm 252 pulls the link 266 rearwardly and pivots the upper front portion of the plate 254 downwardly causing the turn buckle 258 to pivot the hitch assembly 16 downwardly about the pivots 184. As the frame 12 is lowered, the arm 252 moves the link 266 forwardly to pivot the upper front portion of the plate 254 upwardly and raise the hitch assembly 16 about the pivots 184. The hitch connection 18 is thereby maintained at a substantially constant height (FIGS. 7 and 8) above the ground regardless of the position of the frame 12. The turn buckle 258 can be adjusted to initially level the main frame 12. No other leveling adjustment is required for the tillage implement 10. Substantially all of the wheel lift and frame leveling structure is located below the top of the main frame 12. 
     As best seen in FIG. 1, the hitch beams 200 lie generally parallel to the axes of the diagonal beam members 162 to distribute draft forces along the backbone of the main frame 12 which includes the members 162 and the interconnecting beams 164 and 166 of the weldment 160. The diagonal beam members 162 provide substantial added frame strength without decreasing frame-to-ground clearance and without limiting the distance that the gang assemblies 20 can rock upwardly. 
     Fore-and-aft extending side frame members 270 are connected to the transverse beams 120, 142 and 140 by bolts 272 (FIGS. 6 and 14) extending through plates 274 welded to the ends of the beams. In the embodiment of FIG. 1, the stub-bars 110 for the outermost trash-sizing gang assemblies 20 are bolted to the side frame members 270. The extension frames 150 at the rear of the main frame 12 are also connected to the members 270. The stub-bars 110 for the innermost gang assemblies 20 are connected to the diagonal interconnecting beams 164 of the subframe 160. As shown in FIG. 1, a combination of a five-disk gang and a six-disk gang assembly is utilized on each half of the main frame 12, but different combinations of gang assembly widths may be attached to the frame to vary the effective working width. For example, FIG. 9 shows a four-disk and a six-disk gang assembly combination wherein the stub-bars 110 are connected to the fore-and-aft beam 168 to provide a narrower effective width than that of the implement shown in FIG. 1. The extension frame 150 for the configuration of FIG. 9 is single stub-bar which supports one earth-working tool 22 rearwardly of the outermost disks 28. 
     FIG. 10 shows center frame structure similar to that shown in FIG. 9 but hingedly connecting an outrigger frame 300 which is connected for rocking with respect to the main frame 12 by conventional folding hinge structure (not shown). The outrigger frame 300 includes fore-and-aft extending side beams 302 connected by transverse beam members 304, 306 and 308 which are substantially aligned with the transverse beams 120, 142 and 140, respectively, of the main frame 12. A beam 312 extends in the fore-and-aft direction between the beams 304 and 306 and supports a stub-bar 314 and one end of a bar 316. The opposite end of the bar 316 is connected to the beam 302. A four-disk gang assembly 20 is connected to the bars 314 and 316 at an acute angle with respect to the transverse direction. Another four-disk gang assembly 20 is connected to stub-bar 320 and cross member 322 connected to the outer beam 302. To minimize side forces on the outrigger frame 300, the gangs 20 are angled at opposite angles with respect to the transverse direction. Preferably the angle that each disk gang assembly 22 forms with the transverse direction is approximately fourteen degrees. 
     The outrigger frame 300 includes a separate gauge wheel assembly 330 for maintaining the outrigger frame the desired distance above the surface of the ground. 
     In the embodiment shown in FIG. 11, an outrigger frame 340 is connected to the main frame 12 by a folding hinge (not shown). The folding hinge is locked to maintain the outrigger 340 level with the main frame 12 during field-working operations. A total of thirteen disks 28 are transversely spaced on the three gang assemblies 20. The outrigger gang assembly 20 is supported from a cross-member 342 connected between a pair of transversely spaced beams 344 generally parallel and equal in length to the frame member 270. 
     In the embodiment shown in FIG. 12, nine-coulter gang assemblies 20a are supported from the main frame 12 and from a long stub-frame 350 connected to the beam 270. The embodiment of FIG. 12 exemplifies the use of three spring bracket assemblies 42 with a large gang assembly 20. FIG. 13 shows an implement similar to that shown in FIG. 12 but having a narrower effective field-working width with fewer coulters spaced across each half of the front portion of the frame 12. No extension frame or outer stub-bar is required for attaching the earth-working tools 22 in the configuration shown in FIG. 13. 
     It is apparent from FIGS. 1 and 9-13 that numerous field-working widths can be achieved utilizing different combinations of gang assembly widths. These embodiments are given by way of example only to show the versatility provided by the present invention and are not intended to limit the invention strictly to the configurations shown. 
     As best seen in FIG. 1 the trash-sizing gang assemblies 20 and the earth-working tools 22 are substantially symmetrically arranged with respect to the fore-and-aft center line of the implement 10. In the embodiment shown therein, two earth-working tools 22 extend rearwardly from the third beam 142 between the diagonal beam members 162, while only a single earth-working tool 22 is centrally located between the transverse beams 140 and 144 at the rear of the frame 12. A generally open accomodation space is therefore provided between the beams 140 and 144 inwardly of the beam members 162. The inwardmost pair of tools 22 supported on the rear beam 140 are spaced apart a distance substantially equal to the distance between the rear of the diagonal beam members 162 to provide convenient access to the space between the beams 162. Weights 350 can be selectively added to or removed from the rear portions of the beam members 162 to increase or decrease the down pressure on the individual tools 22. As best seen in FIG. 15, the weights 350 are suitcase-type tractor weights which are mounted directly on the beam members 162 and extend inwardly therefrom into the accommodation space. Because the central rear area of the implement 10 is relatively unencumbered with tools 22, the weights 350 can be easily added or removed for different soil conditions. The spring bracket assemblies 42 of the trash-sizing gang assemblies 20 maintain a generally constant down pressure of the gangs 26 against the soil independently of the number of weights 350 added to or removed from the main frame 12. 
     Having described the preferred embodiment, it will be apparent that modifications can be made without departing from the scope of the invention as defined in the accompanying claims.